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RSS2023 Vol. 42, No. 3
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2023, 42(3): 329-337.
doi: 10.13433/j.cnki.1003-8728.20200589
PDF 2220KB
Abstract:
It is technically difficult to develop a wheel-legged robot in complex terrains with the efficient mobile strategy. Based on the conventional mobile strategy, this paper introduces the number of states of joint space to describe the position and posture of the wheel-legs of the robot relative to its body, and the position and posture conversion amount is introduced to describe the motion process between the numbers of adjacent temporal states. Then, the model of the mobile strategy with time consumption and energy consumption considered is established. Taking the shortest mobile time and the lowest energy consumption as goals, the optimization model of the mobile strategy is established, and the efficient mobile strategy for the wheel-legged robot is developed through optimization iteration. The simulation results on the wheel-legged robot crossing obstacles in complex terrains show that the efficient mobile strategy for the wheel-legged robot can successfully complete its obstacle crossing. Compared with the conventional mobile strategy, the mobile time and energy consumption are significantly reduced, verifying that the efficient mobile strategy is effective.
It is technically difficult to develop a wheel-legged robot in complex terrains with the efficient mobile strategy. Based on the conventional mobile strategy, this paper introduces the number of states of joint space to describe the position and posture of the wheel-legs of the robot relative to its body, and the position and posture conversion amount is introduced to describe the motion process between the numbers of adjacent temporal states. Then, the model of the mobile strategy with time consumption and energy consumption considered is established. Taking the shortest mobile time and the lowest energy consumption as goals, the optimization model of the mobile strategy is established, and the efficient mobile strategy for the wheel-legged robot is developed through optimization iteration. The simulation results on the wheel-legged robot crossing obstacles in complex terrains show that the efficient mobile strategy for the wheel-legged robot can successfully complete its obstacle crossing. Compared with the conventional mobile strategy, the mobile time and energy consumption are significantly reduced, verifying that the efficient mobile strategy is effective.
2023, 42(3): 338-344.
doi: 10.13433/j.cnki.1003-8728.20200629
Abstract:
In this paper, a multi-band gap joint phononic crystal filter beam is proposed, which is includes Bragg Diffraction, entire local resonance and partial local resonance. By means of Transfer Matrix and Bloch theorem, it is found that the band gaps of infinite periodic structures are 0 ~ 170 Hz, 180 ~ 262.6 Hz, 552.3 ~ 597 Hz, 974 ~ 1 563 Hz and 1 903 ~ 2 667 Hz. And the modulating law and mechanism of band gap are obtained by changing the structural parameters. At the same time, compared with the band gap characteristics of the traditional three-component and other three working conditions, it is proved that the phononic crystal filter beam has relative advantages in band gap width, richness and elastic wave attenuation rate. That’ to say, phononic crystal filter beam has better performance of filtering and suppressing elastic waves in the structure. In addition, the vibration transfer coefficient of near-phononic crystal filter beam is calculated, and it is concluded that the elastic wave propagation attenuates obviously in the range of each band gap, which verifies the existence of the band gap. In the last part, in order to find out the wave modes of elastic wave in the band gap and in the passband range, the displacement distribution of the beam in band gap and passband range is extracted respectively.From the result, it is found that the elastic wave in band gap frequency range attenuates rapidly along the wave direction, showing the characteristics of band gap. While the elastic wave in the frequency range of passband has no obvious change or attenuation, showing the characteristics of passband. To sum up, this structure provides a new idea and theoretical support for the subsequent apply of phononic crystals to reduce vibration and noise of beam structures.
In this paper, a multi-band gap joint phononic crystal filter beam is proposed, which is includes Bragg Diffraction, entire local resonance and partial local resonance. By means of Transfer Matrix and Bloch theorem, it is found that the band gaps of infinite periodic structures are 0 ~ 170 Hz, 180 ~ 262.6 Hz, 552.3 ~ 597 Hz, 974 ~ 1 563 Hz and 1 903 ~ 2 667 Hz. And the modulating law and mechanism of band gap are obtained by changing the structural parameters. At the same time, compared with the band gap characteristics of the traditional three-component and other three working conditions, it is proved that the phononic crystal filter beam has relative advantages in band gap width, richness and elastic wave attenuation rate. That’ to say, phononic crystal filter beam has better performance of filtering and suppressing elastic waves in the structure. In addition, the vibration transfer coefficient of near-phononic crystal filter beam is calculated, and it is concluded that the elastic wave propagation attenuates obviously in the range of each band gap, which verifies the existence of the band gap. In the last part, in order to find out the wave modes of elastic wave in the band gap and in the passband range, the displacement distribution of the beam in band gap and passband range is extracted respectively.From the result, it is found that the elastic wave in band gap frequency range attenuates rapidly along the wave direction, showing the characteristics of band gap. While the elastic wave in the frequency range of passband has no obvious change or attenuation, showing the characteristics of passband. To sum up, this structure provides a new idea and theoretical support for the subsequent apply of phononic crystals to reduce vibration and noise of beam structures.
2023, 42(3): 345-351.
doi: 10.13433/j.cnki.1003-8728.20200581
Abstract:
To study the influence of different structural parameters on the low-speed dynamic impact response of two aluminum honeycomb sandwich panels that have the same mass and different strength, the numerical model of the aluminum honeycomb sandwich panel subjected to the low-speed impact of a half-ball drop hammer was established. The results on its finite element calculation and test were compared to verify the reliability of the model. On this basis, the effects of different upper and lower aluminum panel thickness and honeycomb core wall thickness on the energy absorption of the aluminum honeycomb sandwich panel under low-speed impact were studied. The results show that, under the condition of the same mass, the force-displacement curve of the sandwich panel with small strength and large height is more likely to appear in the bimodal mode under low-speed impact. Increasing the honeycomb core wall thickness or the upper and lower aluminum panel thickness may increase the first peak force but reduce the second peak force. The honeycomb core of the sandwich panel with small strength but large height occupies more energy absorption ratio in low-speed impact, while the upper aluminum panel with large strength but small height absorbs more energy, and the mass and volume of the former are higher than the energy absorption ratio of the latter. The mass and volume specific energy absorption ratio of the aluminum honeycomb sandwich panel is dependent on the ratio of wall thickness to side length and the ratio of plate thickness to core thickness.
To study the influence of different structural parameters on the low-speed dynamic impact response of two aluminum honeycomb sandwich panels that have the same mass and different strength, the numerical model of the aluminum honeycomb sandwich panel subjected to the low-speed impact of a half-ball drop hammer was established. The results on its finite element calculation and test were compared to verify the reliability of the model. On this basis, the effects of different upper and lower aluminum panel thickness and honeycomb core wall thickness on the energy absorption of the aluminum honeycomb sandwich panel under low-speed impact were studied. The results show that, under the condition of the same mass, the force-displacement curve of the sandwich panel with small strength and large height is more likely to appear in the bimodal mode under low-speed impact. Increasing the honeycomb core wall thickness or the upper and lower aluminum panel thickness may increase the first peak force but reduce the second peak force. The honeycomb core of the sandwich panel with small strength but large height occupies more energy absorption ratio in low-speed impact, while the upper aluminum panel with large strength but small height absorbs more energy, and the mass and volume of the former are higher than the energy absorption ratio of the latter. The mass and volume specific energy absorption ratio of the aluminum honeycomb sandwich panel is dependent on the ratio of wall thickness to side length and the ratio of plate thickness to core thickness.
2023, 42(3): 352-357.
doi: 10.13433/j.cnki.1003-8728.20200586
Abstract:
To analyze the flow field characteristics of the wind field under the action of the porous jet fan, the CFD method is used to simulate the internal flow field of the porous jet wind field model, and the effects of the number and arrangement of nozzles on the flow field performance are compared and analyzed. The theory of vortex dynamics is introduced to analyze the distribution and development of vortex structure in the flow field and its influence on fluid mixing effect. The simulation results show that the arrangement of nozzles has a significant impact on the flow field performance, and the peripheral nozzles will restrict the flow of the central nozzle; the streamwise vortex has a greater effect on the fluid mixing effect than the spanwise vortex. In the case of a constant vortex, a larger flow vortex scale and faster attenuation is advantageous to the flow field stability. The velocity and vortex dynamics distribution in the flow field show that the stability of the flow field increases significantly with the increase of the number of nozzles. Therefore, the number of nozzle arrangements should be used as much as possible on the premise of ensuring economy.
To analyze the flow field characteristics of the wind field under the action of the porous jet fan, the CFD method is used to simulate the internal flow field of the porous jet wind field model, and the effects of the number and arrangement of nozzles on the flow field performance are compared and analyzed. The theory of vortex dynamics is introduced to analyze the distribution and development of vortex structure in the flow field and its influence on fluid mixing effect. The simulation results show that the arrangement of nozzles has a significant impact on the flow field performance, and the peripheral nozzles will restrict the flow of the central nozzle; the streamwise vortex has a greater effect on the fluid mixing effect than the spanwise vortex. In the case of a constant vortex, a larger flow vortex scale and faster attenuation is advantageous to the flow field stability. The velocity and vortex dynamics distribution in the flow field show that the stability of the flow field increases significantly with the increase of the number of nozzles. Therefore, the number of nozzle arrangements should be used as much as possible on the premise of ensuring economy.
2023, 42(3): 358-366.
doi: 10.13433/j.cnki.1003-8728.20200594
Abstract:
Under the influence of internal fluid and Coriolis force generated by rotation, the drilling string easily brings about coupled vibration, causing serious accidents such as fatigue failure. Based on the differential quadrature method (DQM), this paperstudiedthe dynamic characteristics of the drilling string in a horizontal well with two-phase flow affected by multiple factors. Using the extended Hamilton variational principle, the dynamics equation for thedrill stringis established that takes into account the influence factors such as internal fluid, axial pressure and rotation. The generalized boundary condition is used to solve the vibration problem. The boundary condition model is simplified, and the cantilever is supported by changing the stiffness of the boundary equivalent spring. By analyzing the influence factors such as rotational angular velocity, axial pressure, fluid velocity, gas volume fraction and other factors on the frequency characteristics of the model, the characteristic curve of the dimensionless natural frequency with different parameters are obtained. The analysis results show that: the frequency characteristic curve of the model under different boundary conditions is very different; the influence of gas volume fraction on critical flow velocity is more obvious in the cantilever pipe system; with the simply supported pipe system, as the axial pressure increases, the cantilever pipe system may exhibit modal coupling flutter. In addition, the frequency cloud diagram of the fluid velocity and the rotational angular velocity demonstrates the influence of the two factors on the frequency characteristics of the drilling string.
Under the influence of internal fluid and Coriolis force generated by rotation, the drilling string easily brings about coupled vibration, causing serious accidents such as fatigue failure. Based on the differential quadrature method (DQM), this paperstudiedthe dynamic characteristics of the drilling string in a horizontal well with two-phase flow affected by multiple factors. Using the extended Hamilton variational principle, the dynamics equation for thedrill stringis established that takes into account the influence factors such as internal fluid, axial pressure and rotation. The generalized boundary condition is used to solve the vibration problem. The boundary condition model is simplified, and the cantilever is supported by changing the stiffness of the boundary equivalent spring. By analyzing the influence factors such as rotational angular velocity, axial pressure, fluid velocity, gas volume fraction and other factors on the frequency characteristics of the model, the characteristic curve of the dimensionless natural frequency with different parameters are obtained. The analysis results show that: the frequency characteristic curve of the model under different boundary conditions is very different; the influence of gas volume fraction on critical flow velocity is more obvious in the cantilever pipe system; with the simply supported pipe system, as the axial pressure increases, the cantilever pipe system may exhibit modal coupling flutter. In addition, the frequency cloud diagram of the fluid velocity and the rotational angular velocity demonstrates the influence of the two factors on the frequency characteristics of the drilling string.
2023, 42(3): 367-374.
doi: 10.13433/j.cnki.1003-8728.20200591
Abstract:
In order to improve the energy regeneration effect and dynamic performance of the energy regeneration suspension system, a new vehicle electro-hydraulic energy regeneration interconnected suspension structure is proposed in this paper. According to the relationship between flow and pressure drop of electro-hydraulic energy regeneration system, the coupled mathematical models oftheoverall vehicle with 7 degrees of freedom and the electro-hydraulic energy regeneration interconnected suspension system are established, and the damping characteristics and energy regeneration characteristics of the vehicle electro-hydraulic energy regeneration interconnected suspension are simulated through sinusoidal excitation. Takingstochastic road as input, the vehicle's ride comfort and driving stability are simulated and analyzed. The results show that the damping force and the energyregeneration power are proportional to the frequency and amplitude of excitation, and the fluctuation of the energyregeneration power is inversely proportional to them; the energyregeneration efficiency first increases and then decreases with the increase of the amplitude and frequency. On stochastic road, compared with passive suspension, the pitch mode and roll mode of the electro-hydraulic energyregeneration interconnected suspension can improve the vehicle'sdynamic performance while realizing the recovery of vibration energy.
In order to improve the energy regeneration effect and dynamic performance of the energy regeneration suspension system, a new vehicle electro-hydraulic energy regeneration interconnected suspension structure is proposed in this paper. According to the relationship between flow and pressure drop of electro-hydraulic energy regeneration system, the coupled mathematical models oftheoverall vehicle with 7 degrees of freedom and the electro-hydraulic energy regeneration interconnected suspension system are established, and the damping characteristics and energy regeneration characteristics of the vehicle electro-hydraulic energy regeneration interconnected suspension are simulated through sinusoidal excitation. Takingstochastic road as input, the vehicle's ride comfort and driving stability are simulated and analyzed. The results show that the damping force and the energyregeneration power are proportional to the frequency and amplitude of excitation, and the fluctuation of the energyregeneration power is inversely proportional to them; the energyregeneration efficiency first increases and then decreases with the increase of the amplitude and frequency. On stochastic road, compared with passive suspension, the pitch mode and roll mode of the electro-hydraulic energyregeneration interconnected suspension can improve the vehicle'sdynamic performance while realizing the recovery of vibration energy.
2023, 42(3): 375-381.
doi: 10.13433/j.cnki.1003-8728.20200612
Abstract:
Taking the cycloid needle wheel ofthe heavy load RV reducer as the research object, the finite element analysis software is used to establish the gear tooth contact equivalent model, and the contact stress distribution of the cycloid wheel tooth surface is obtained and its maximum contact stress area is analyzed. Based on the rigid-flexible coupling dynamics modeling, the stress-time history of the maximum contact stress area is obtained. In terms of the fatigue cumulative damage theory, the final life of the cycloid needle wheel under the corresponding external cyclic load is analyzed with the finite element results via special fatigue life simulation software and load spectrum as input. The results show that the maximum stress position of the cycloid wheel and the dangerous part is near the index circle and close to the end face, the maximum stress is 817 MPa, the fatigue life is 106.673 times, and the equivalent life is 5 233 h, which provides the reference value for the anti-fatigue optimization design of the cycloid wheel.
Taking the cycloid needle wheel ofthe heavy load RV reducer as the research object, the finite element analysis software is used to establish the gear tooth contact equivalent model, and the contact stress distribution of the cycloid wheel tooth surface is obtained and its maximum contact stress area is analyzed. Based on the rigid-flexible coupling dynamics modeling, the stress-time history of the maximum contact stress area is obtained. In terms of the fatigue cumulative damage theory, the final life of the cycloid needle wheel under the corresponding external cyclic load is analyzed with the finite element results via special fatigue life simulation software and load spectrum as input. The results show that the maximum stress position of the cycloid wheel and the dangerous part is near the index circle and close to the end face, the maximum stress is 817 MPa, the fatigue life is 106.673 times, and the equivalent life is 5 233 h, which provides the reference value for the anti-fatigue optimization design of the cycloid wheel.
2023, 42(3): 382-387.
doi: 10.13433/j.cnki.1003-8728.20200646
Abstract:
In this paper, a numerical simulation model of a vehicle's aerodynamic flow field was established, and the generation and development processes of water phase were simulated with the Lagrangian discrete phase model and the Eulerian wall film model. On this basis, the formation of water phase on the body surface under different rainfall intensity and velocity was calculated, and the factors affecting the distribution of water phase were studied. The results show that under certain conditions of velocity and rainfall intensity, the thickness of water phase gradually increases and finally becomes stable. When the velocity is constant, the thickness of water phase in the front window, rear window and side window increases with the increase of rainfall intensity. When the rainfall intensity is constant, the water phase thickness on the front window, rear window and side window increases with the increase of vehicle velocity, while the water phase thickness on the front window decreases with the increase of vehicle velocity.
In this paper, a numerical simulation model of a vehicle's aerodynamic flow field was established, and the generation and development processes of water phase were simulated with the Lagrangian discrete phase model and the Eulerian wall film model. On this basis, the formation of water phase on the body surface under different rainfall intensity and velocity was calculated, and the factors affecting the distribution of water phase were studied. The results show that under certain conditions of velocity and rainfall intensity, the thickness of water phase gradually increases and finally becomes stable. When the velocity is constant, the thickness of water phase in the front window, rear window and side window increases with the increase of rainfall intensity. When the rainfall intensity is constant, the water phase thickness on the front window, rear window and side window increases with the increase of vehicle velocity, while the water phase thickness on the front window decreases with the increase of vehicle velocity.
2023, 42(3): 388-395.
doi: 10.13433/j.cnki.1003-8728.20200596
Abstract:
An optimal trajectory planning method based on improved whale optimization algorithm is proposed in order to solve the time optimal trajectory planning problem of manipulator. Firstly, the trajectory of the manipulator is constructed by quintic polynomial interpolation in the joint space with the constrains in the kinematic limits of velocity, acceleration, and jerk. Then, the objective function is established to minimize the running time of the manipulator and the improved whale optimization algorithm (IWOA) is used to optimize the time to improve the operation efficiency of the manipulator. Finally, the MATLAB simulation results show that the improved whale optimization algorithm has higher solvingaccuracy and faster convergence speed than other similar algorithms, and the displacement, velocity and acceleration curves of the manipulator which were obtained by combining IWOA and trajectory optimization are smooth without obvious mutation, which verifies the effectiveness of the proposed trajectory planning method.
An optimal trajectory planning method based on improved whale optimization algorithm is proposed in order to solve the time optimal trajectory planning problem of manipulator. Firstly, the trajectory of the manipulator is constructed by quintic polynomial interpolation in the joint space with the constrains in the kinematic limits of velocity, acceleration, and jerk. Then, the objective function is established to minimize the running time of the manipulator and the improved whale optimization algorithm (IWOA) is used to optimize the time to improve the operation efficiency of the manipulator. Finally, the MATLAB simulation results show that the improved whale optimization algorithm has higher solvingaccuracy and faster convergence speed than other similar algorithms, and the displacement, velocity and acceleration curves of the manipulator which were obtained by combining IWOA and trajectory optimization are smooth without obvious mutation, which verifies the effectiveness of the proposed trajectory planning method.
2023, 42(3): 396-401.
doi: 10.13433/j.cnki.1003-8728.20230081
Abstract:
A set of constant tension control system is designed according to the winding quality requirements of narrow-band metal strip. The tension generation and its influencing factors in the process control of metal narrow strip winding production are analyzed. On the basis of maintaining constant tension control, a double closed loop, cascade and dynamic control system for narrow strip winding is proposed, designed and manufactured. The system uses single chip microcomputer as the core control unit to realize signal acquisition and control signal output. With three-phase AC torque motor as the main actuator, combined with double closed-loop control of speed and tension, a controllable constant tension mechanism for strip winding based on torque motor is realized. At the same time, a stepper motor is used as auxiliary actuator and displacement detection is used as feedback to control the coiling mechanism move horizontally. In addition, a kind of feed-forward control mode is designed with the thickness of metal strip as feed-forward signal. After circuit diagrams are designed, circuit boards are made, the system is integrated. The application of the system shows that the winding process of the strip is uniform in force, stable in tension, appropriate in turn-to-turn clearance, moderate in tension between layers, smooth and uniform in winding, which ensures the production quality.
A set of constant tension control system is designed according to the winding quality requirements of narrow-band metal strip. The tension generation and its influencing factors in the process control of metal narrow strip winding production are analyzed. On the basis of maintaining constant tension control, a double closed loop, cascade and dynamic control system for narrow strip winding is proposed, designed and manufactured. The system uses single chip microcomputer as the core control unit to realize signal acquisition and control signal output. With three-phase AC torque motor as the main actuator, combined with double closed-loop control of speed and tension, a controllable constant tension mechanism for strip winding based on torque motor is realized. At the same time, a stepper motor is used as auxiliary actuator and displacement detection is used as feedback to control the coiling mechanism move horizontally. In addition, a kind of feed-forward control mode is designed with the thickness of metal strip as feed-forward signal. After circuit diagrams are designed, circuit boards are made, the system is integrated. The application of the system shows that the winding process of the strip is uniform in force, stable in tension, appropriate in turn-to-turn clearance, moderate in tension between layers, smooth and uniform in winding, which ensures the production quality.
2023, 42(3): 402-407.
doi: 10.13433/j.cnki.1003-8728.20200579
Abstract:
The energy-harvesting suspension can realize the harvesting of vibration energy while completing the relevant functions of passive suspension. This paper proposes a magnetic energy-harvesting suspension structure, which is based on the original passive suspension spring and the damping structure and incorporated with the energy-harvesting element of the Faraday law of electromagnetic induction to ensure the safety of the original passive suspension and to realize the energy-harvesting function of no-contact, no-friction and no-lubrication. It also describes the principles and basic structures of the energy-harvesting suspension and then optimizes its structure. Then, the prototype of the magnetic energy-harvesting suspension and its bench were developed to study its output voltage characteristics under variable frequency and variable amplitude sinusoidal excitation. The experimental results show that the output voltage of the magnetic energy-harvesting suspension is positively correlated with the amplitude and frequency of the sinusoidal excitation. In order to verify the feasibility of the self-powered suspension, a sensor is selected as the load. Under the sine excitation of 7 Hz and 4 mm, the suspension can continuously output a voltage of 22 V to successfully power the sensor.
The energy-harvesting suspension can realize the harvesting of vibration energy while completing the relevant functions of passive suspension. This paper proposes a magnetic energy-harvesting suspension structure, which is based on the original passive suspension spring and the damping structure and incorporated with the energy-harvesting element of the Faraday law of electromagnetic induction to ensure the safety of the original passive suspension and to realize the energy-harvesting function of no-contact, no-friction and no-lubrication. It also describes the principles and basic structures of the energy-harvesting suspension and then optimizes its structure. Then, the prototype of the magnetic energy-harvesting suspension and its bench were developed to study its output voltage characteristics under variable frequency and variable amplitude sinusoidal excitation. The experimental results show that the output voltage of the magnetic energy-harvesting suspension is positively correlated with the amplitude and frequency of the sinusoidal excitation. In order to verify the feasibility of the self-powered suspension, a sensor is selected as the load. Under the sine excitation of 7 Hz and 4 mm, the suspension can continuously output a voltage of 22 V to successfully power the sensor.
Study on Numerical Simulation and Residual Stress in Multi-channel and Multi-layer Surfacing Welding
2023, 42(3): 408-414.
doi: 10.13433/j.cnki.1003-8728.20200615
Abstract:
In this paper, the multi-channel and multi-layer surfacing welding process of Superalloy was simulated via Marc finite element analysis software. The effect of the surfacing thickness and surfacing path on the residual stress after surfacing welding was emphatically discussed. The results showed that in the surfacing welding, the increase in surfacing thickness would lead to the increase in the peak value of the transverse residual stress and the change of the local stress direction inside the welding bead, which results in the surfacing layers are subjected to multi-directional stress. Therefore, on the premise of meeting the use requirements, the surfacing thickness is not suitable to be too large. And because of the influence of the temperature of the front and latter layers, there was a phenomenon of stress release between the surfacing layers. In addition, the residual stress distribution in the process of "channel-by-channel surfacing" and "layer-by-layer surfacing" were compared. The residual stress distribution of "layer-by-layer surfacing" was more uniform than that of "channel-by-channel surfacing", and the peak value of residual stress was smaller.
In this paper, the multi-channel and multi-layer surfacing welding process of Superalloy was simulated via Marc finite element analysis software. The effect of the surfacing thickness and surfacing path on the residual stress after surfacing welding was emphatically discussed. The results showed that in the surfacing welding, the increase in surfacing thickness would lead to the increase in the peak value of the transverse residual stress and the change of the local stress direction inside the welding bead, which results in the surfacing layers are subjected to multi-directional stress. Therefore, on the premise of meeting the use requirements, the surfacing thickness is not suitable to be too large. And because of the influence of the temperature of the front and latter layers, there was a phenomenon of stress release between the surfacing layers. In addition, the residual stress distribution in the process of "channel-by-channel surfacing" and "layer-by-layer surfacing" were compared. The residual stress distribution of "layer-by-layer surfacing" was more uniform than that of "channel-by-channel surfacing", and the peak value of residual stress was smaller.
2023, 42(3): 415-425.
doi: 10.13433/j.cnki.1003-8728.20200567
Abstract:
An explicit model predictive cross-coupled control (EMPCCC) method is proposed to improve the contour trajectory tracking accuracy and the dynamic performance of the system driven by a permanent magnet synchronous linear motor.The method combines the explicit predictive control with cross-coupling control to perform multi-step prediction of single-axis current and velocity signals, and use the contour error as a feedback quantity to correct the given trajectory of the predictive control to achieve the purpose of contour error predictive control.Finally, the simulation model is built based on MATLAB/Simulink, and the simulation results show that the EMPCCC method can quickly achieve overshoot-free tracking control of different speed waveforms, and it can estimate and compensate the contour error to improve the contour accuracy of different trajectories.
An explicit model predictive cross-coupled control (EMPCCC) method is proposed to improve the contour trajectory tracking accuracy and the dynamic performance of the system driven by a permanent magnet synchronous linear motor.The method combines the explicit predictive control with cross-coupling control to perform multi-step prediction of single-axis current and velocity signals, and use the contour error as a feedback quantity to correct the given trajectory of the predictive control to achieve the purpose of contour error predictive control.Finally, the simulation model is built based on MATLAB/Simulink, and the simulation results show that the EMPCCC method can quickly achieve overshoot-free tracking control of different speed waveforms, and it can estimate and compensate the contour error to improve the contour accuracy of different trajectories.
2023, 42(3): 426-431.
doi: 10.13433/j.cnki.1003-8728.20200564
Abstract:
Compliance matrix modeling is the basis for analyzing the fully flexible mechanisms. For the 3-PSS type flexible parallel micro-manipulation robot, the compliance matrix of a single branch of the mechanism is calculated based on the coordinate transformation method, and the overall compliance matrix model for robot is established. Then, numerical calculation examples and ANSYS finite element simulation analysis are performed, and the calculated results are compared with the finite element analysis results to verify the correctness of the compliance matrix modeling. Finally, the flexibility performance of the flexible parallel robots is analyzed, and the influence of the structure parameters of the mechanism on the flexibility is obtained. The analysis results provide a basis for the structural optimization design of the 3-PSS flexible parallel mechanism.
Compliance matrix modeling is the basis for analyzing the fully flexible mechanisms. For the 3-PSS type flexible parallel micro-manipulation robot, the compliance matrix of a single branch of the mechanism is calculated based on the coordinate transformation method, and the overall compliance matrix model for robot is established. Then, numerical calculation examples and ANSYS finite element simulation analysis are performed, and the calculated results are compared with the finite element analysis results to verify the correctness of the compliance matrix modeling. Finally, the flexibility performance of the flexible parallel robots is analyzed, and the influence of the structure parameters of the mechanism on the flexibility is obtained. The analysis results provide a basis for the structural optimization design of the 3-PSS flexible parallel mechanism.
2023, 42(3): 432-438.
doi: 10.13433/j.cnki.1003-8728.20200648
Abstract:
Aiming at the problem that the traditional design method with the goal of the general layout cannot fully meet the reliability requirements of the exhaust system. In this paper, we propose a new design method ofoptimizing the reliability of exhaust systems based on an improved ant colony algorithm. The traditional ant colony algorithm is improved by optimizing the probability factor, the dynamic processing mechanism of volatile conditions and the introduction to a max-min ant system. A reliability life prediction model is constructed by combining CAE simulation, stress spectrum acquisition and quadratic response surface fitting method, and the improved ant colony algorithm is used to solve the optimal design. The results show that the maximum stress on the exhaust system reduced from 175.11 MPa to 158.92 MPa, and the calculated reliability life increased from 5623.69 h to 6165.95 h. This new method effectively improves the reliability life of the vehicle exhaust system.
Aiming at the problem that the traditional design method with the goal of the general layout cannot fully meet the reliability requirements of the exhaust system. In this paper, we propose a new design method ofoptimizing the reliability of exhaust systems based on an improved ant colony algorithm. The traditional ant colony algorithm is improved by optimizing the probability factor, the dynamic processing mechanism of volatile conditions and the introduction to a max-min ant system. A reliability life prediction model is constructed by combining CAE simulation, stress spectrum acquisition and quadratic response surface fitting method, and the improved ant colony algorithm is used to solve the optimal design. The results show that the maximum stress on the exhaust system reduced from 175.11 MPa to 158.92 MPa, and the calculated reliability life increased from 5623.69 h to 6165.95 h. This new method effectively improves the reliability life of the vehicle exhaust system.
2023, 42(3): 439-445.
doi: 10.13433/j.cnki.1003-8728.20200593
Abstract:
The traditional forming method uses the plane layer only, which cause the low surface accuracy of the parts, aiming at this problem, a novel curved mix-layer slicing method is studied, and a method to detect the overall accuracy of model is proposed. For a model for automatically detection printable surface for curved printing, and the more accurate neighbor-normal mean algorithm is used to calculate the offset surface and generate the plane base layer according to the original model. A collision detection and forming sequence planning process are also included for the complex model, which can generate collision free tool path according to the actual situation of forming equipment. Finally, the comparison results of multiple parts show that curved slicing can greatly improve the surface quality with lower surface roughness and higher overall accuracy.
The traditional forming method uses the plane layer only, which cause the low surface accuracy of the parts, aiming at this problem, a novel curved mix-layer slicing method is studied, and a method to detect the overall accuracy of model is proposed. For a model for automatically detection printable surface for curved printing, and the more accurate neighbor-normal mean algorithm is used to calculate the offset surface and generate the plane base layer according to the original model. A collision detection and forming sequence planning process are also included for the complex model, which can generate collision free tool path according to the actual situation of forming equipment. Finally, the comparison results of multiple parts show that curved slicing can greatly improve the surface quality with lower surface roughness and higher overall accuracy.
2023, 42(3): 446-452.
doi: 10.13433/j.cnki.1003-8728.20200583
Abstract:
A rolling bearing fault diagnosis method based on variational mode decomposition (VMD) combined with time-shift multiscale dispersion entropy(TSMDE) fault feature extraction and improved bat algorithm (IBA) in order to optimize support vector machine (SVM)was proposed. Firstly, the problem of mode aliasing was avoidedby means of variational mode decomposition, and the dispersion entropy of each modal component was extracted to construct the fault feature vector, which was used as the input of the fault diagnosis model. Then, a new adaptive speed weight factor was proposed to construct an improved bat algorithm for optimizing support vector machine (IBA-SVM), and the bearings with different fault typeswereclassified. Finally, the experimental data were used to verify the proposed diagnostic method and compared with the particle swarm optimization support vector machine (PSO-SVM) method. The results show that the proposed method has higher classification accuracy and less time.
A rolling bearing fault diagnosis method based on variational mode decomposition (VMD) combined with time-shift multiscale dispersion entropy(TSMDE) fault feature extraction and improved bat algorithm (IBA) in order to optimize support vector machine (SVM)was proposed. Firstly, the problem of mode aliasing was avoidedby means of variational mode decomposition, and the dispersion entropy of each modal component was extracted to construct the fault feature vector, which was used as the input of the fault diagnosis model. Then, a new adaptive speed weight factor was proposed to construct an improved bat algorithm for optimizing support vector machine (IBA-SVM), and the bearings with different fault typeswereclassified. Finally, the experimental data were used to verify the proposed diagnostic method and compared with the particle swarm optimization support vector machine (PSO-SVM) method. The results show that the proposed method has higher classification accuracy and less time.
2023, 42(3): 453-461.
doi: 10.13433/j.cnki.1003-8728.20200558
Abstract:
The parallel mechanism 2T1R was taken as the research object, based on the topological structure design theory of parallel mechanism, a kind of 2T1R parallel mechanism with Pa parallelogram and branch chain is synthesized, and two new types of 2PRPaR-PPaR and 2RRPaR-PPaR parallel mechanisms are selected. Taking 2PRPaR-PPaR parallel mechanism as an example, the topological characteristics of mechanism such as azimuth feature set, degree of freedom and coupling degree are calculated by using the topological structure theory of azimuth feature set. The inverse kinematics solution of the mechanism is obtained based on the established characteristic equation. Based on this, the performance indexes of the mechanism, such as workspace, dexterity and rotation ability, are visualized and analyzed respectively, and the influence of the mechanism parameters on these performance indexes is analyzed through the graphical comparison. Finally, the multi-objective optimization model of workspace and global dexterity is established, and the fast non dominated multi-objective optimization algorithm (NSGA -Ⅱ) is selected to realize the scale synthesis of mechanism. The results show that 2 PRPaR-PPaR mechanism has the advantages of large workspace, good dexterity and high rotation ability, and a set of multi-objective Pareto optimization solutions for workspace and global dexterity under different attitude angles are optimized out.
The parallel mechanism 2T1R was taken as the research object, based on the topological structure design theory of parallel mechanism, a kind of 2T1R parallel mechanism with Pa parallelogram and branch chain is synthesized, and two new types of 2PRPaR-PPaR and 2RRPaR-PPaR parallel mechanisms are selected. Taking 2PRPaR-PPaR parallel mechanism as an example, the topological characteristics of mechanism such as azimuth feature set, degree of freedom and coupling degree are calculated by using the topological structure theory of azimuth feature set. The inverse kinematics solution of the mechanism is obtained based on the established characteristic equation. Based on this, the performance indexes of the mechanism, such as workspace, dexterity and rotation ability, are visualized and analyzed respectively, and the influence of the mechanism parameters on these performance indexes is analyzed through the graphical comparison. Finally, the multi-objective optimization model of workspace and global dexterity is established, and the fast non dominated multi-objective optimization algorithm (NSGA -Ⅱ) is selected to realize the scale synthesis of mechanism. The results show that 2 PRPaR-PPaR mechanism has the advantages of large workspace, good dexterity and high rotation ability, and a set of multi-objective Pareto optimization solutions for workspace and global dexterity under different attitude angles are optimized out.
2023, 42(3): 462-467.
doi: 10.13433/j.cnki.1003-8728.20200600
Abstract:
In view of the single application situation of existing degradation assessment methods and the reliance on manual experience for feature index screening, a rolling bearing performance degradation assessment method was proposed based on the combination of deep belief network (DBN) and continuous hidden Markov (CHMM). The vibration signals of rolling bearings in normal state were processed into the normalized amplitude spectrum, which was used as the input of DBN feature automatic extraction model, and CHMM was applied as the assessment model, the training set of CHMM is the characteristic vector obtained by DBN under normal state. The whole life cycle experimental data of rolling bearings under different situations was employed to verify the effectiveness of proposed method. Compared with recent literatures, this method avoids manual selection of characteristic index, and has certain sensitivity to early weak fault detection.
In view of the single application situation of existing degradation assessment methods and the reliance on manual experience for feature index screening, a rolling bearing performance degradation assessment method was proposed based on the combination of deep belief network (DBN) and continuous hidden Markov (CHMM). The vibration signals of rolling bearings in normal state were processed into the normalized amplitude spectrum, which was used as the input of DBN feature automatic extraction model, and CHMM was applied as the assessment model, the training set of CHMM is the characteristic vector obtained by DBN under normal state. The whole life cycle experimental data of rolling bearings under different situations was employed to verify the effectiveness of proposed method. Compared with recent literatures, this method avoids manual selection of characteristic index, and has certain sensitivity to early weak fault detection.
2023, 42(3): 468-474.
doi: 10.13433/j.cnki.1003-8728.20200631
Abstract:
Aiming at the problem that the Q matrix and R matrix in the LQR control of vehicle semi-active suspensions are often valued by personal experience, an LQR control method based on an improved particle swarm algorithm is proposed. The algorithm uses random inertia weights instead of the fixed inertia weights of the traditional particle swarm algorithm, improves the accuracy and efficiency of the solution, and obtains more adaptive LQR control matrix coefficients. In order to verify the effectiveness of this method, a quarter-car passive suspension model and a semi-active suspension model are established based on the ceiling damping model, the LQR controller is established using linear quadratic optimal control, and the new control matrix is obtained using the optimization algorithm. Through simulation and comparison of various performance parameters of passive suspension, LQR semi-active suspension controlled by LQR, and optimized LQR suspension optimized by improved particle swarm algorithm, it is found that the optimized LQR suspension effectively reduces the vertical acceleration of the vehicle and the dynamic load of the tire on the premise that the dynamic deflection of the suspension is not affected, and improves the driving comfort and handling safety of the vehicle.
Aiming at the problem that the Q matrix and R matrix in the LQR control of vehicle semi-active suspensions are often valued by personal experience, an LQR control method based on an improved particle swarm algorithm is proposed. The algorithm uses random inertia weights instead of the fixed inertia weights of the traditional particle swarm algorithm, improves the accuracy and efficiency of the solution, and obtains more adaptive LQR control matrix coefficients. In order to verify the effectiveness of this method, a quarter-car passive suspension model and a semi-active suspension model are established based on the ceiling damping model, the LQR controller is established using linear quadratic optimal control, and the new control matrix is obtained using the optimization algorithm. Through simulation and comparison of various performance parameters of passive suspension, LQR semi-active suspension controlled by LQR, and optimized LQR suspension optimized by improved particle swarm algorithm, it is found that the optimized LQR suspension effectively reduces the vertical acceleration of the vehicle and the dynamic load of the tire on the premise that the dynamic deflection of the suspension is not affected, and improves the driving comfort and handling safety of the vehicle.
2023, 42(3): 475-483.
doi: 10.13433/j.cnki.1003-8728.20200603
Abstract:
Ion exchange polymer metal composite (IPMC) has both driving and sensing functions. In this paper, based on the sensing ability of IPMC, an ocean current velocity information sensor is designed. Based on the three models, ANSYS and MATLAB software are used to simulate different conditions. A test system was designed to analyze and verify the sensing ability of the IPMC under uniform flow rate. The results show that: the initial stable voltage and measurement sensitivity of IPMC are positively correlated with the material area; the time for IPMC to reach the stable output voltagewith the increasing of flow rate is shortened; before reaching the stable output voltage, the output voltage is a quadratic polynomial function with time, and the maximum value of the function is the measured stable output voltage; the repeatability of each group of experiments is good.
Ion exchange polymer metal composite (IPMC) has both driving and sensing functions. In this paper, based on the sensing ability of IPMC, an ocean current velocity information sensor is designed. Based on the three models, ANSYS and MATLAB software are used to simulate different conditions. A test system was designed to analyze and verify the sensing ability of the IPMC under uniform flow rate. The results show that: the initial stable voltage and measurement sensitivity of IPMC are positively correlated with the material area; the time for IPMC to reach the stable output voltagewith the increasing of flow rate is shortened; before reaching the stable output voltage, the output voltage is a quadratic polynomial function with time, and the maximum value of the function is the measured stable output voltage; the repeatability of each group of experiments is good.
2023, 42(3): 484-490.
doi: 10.13433/j.cnki.1003-8728.20200592
Abstract:
the initial level set function was interpolated by using the radial basis functions with global supports, and the level set functions and weighted function of compliance and heat dissipation were chosen as the design variables and objective function, respectively; and then the thermo-mechanical coupling multi-objective topology optimization model for the orthotropic structure was established based on the parameterized level set method (PLSM). The influence of weight coefficient, off-angle, Poisson's ratio factor and thermal conductivity factor on the multi-objective optimal topological structure and objective function value was studied through numerical examples, and the reasonable range of the above parameters was provided. The performance analysis of the optimal orthotropic topological structure was performed on the basis of 3D printed products, which was compared with that of the isotropic structure. The results show that the profile of PLSM optimal topological structure is smoother and clearer than that of the topological structure based on the variable density method, and there will be no intermediate density and sawtooth. The temperature, displacement and stress field of the orthotropic structure are improved compared with the isotropic structure, and the weighted objective function, compliance and heat dissipation are reduced by 55%, 3.18% and 81.1%, respectively.
the initial level set function was interpolated by using the radial basis functions with global supports, and the level set functions and weighted function of compliance and heat dissipation were chosen as the design variables and objective function, respectively; and then the thermo-mechanical coupling multi-objective topology optimization model for the orthotropic structure was established based on the parameterized level set method (PLSM). The influence of weight coefficient, off-angle, Poisson's ratio factor and thermal conductivity factor on the multi-objective optimal topological structure and objective function value was studied through numerical examples, and the reasonable range of the above parameters was provided. The performance analysis of the optimal orthotropic topological structure was performed on the basis of 3D printed products, which was compared with that of the isotropic structure. The results show that the profile of PLSM optimal topological structure is smoother and clearer than that of the topological structure based on the variable density method, and there will be no intermediate density and sawtooth. The temperature, displacement and stress field of the orthotropic structure are improved compared with the isotropic structure, and the weighted objective function, compliance and heat dissipation are reduced by 55%, 3.18% and 81.1%, respectively.
