Motion Control Study of Two-legged Wheeled Robot
Objective The two-legged wheeled robot is a new type of composite ground mobile robot constituted by designing wheels at the end of the legs of footed robots, which combines the improved maneuverability and flexibility of traditional wheeled mobile platforms and footed robotic structures and has enh...
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| Format: | Article |
| Language: | English |
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Editorial Department of Journal of Sichuan University (Engineering Science Edition)
2024-09-01
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| Series: | 工程科学与技术 |
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| Online Access: | http://jsuese.scu.edu.cn/thesisDetails#10.12454/j.jsuese.202300854 |
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| author | Checao YU Xinzhi MA Xuejun ZHU Xudong YANG Huige LAI Aidi YANG |
| author_facet | Checao YU Xinzhi MA Xuejun ZHU Xudong YANG Huige LAI Aidi YANG |
| author_sort | Checao YU |
| collection | DOAJ |
| description | Objective The two-legged wheeled robot is a new type of composite ground mobile robot constituted by designing wheels at the end of the legs of footed robots, which combines the improved maneuverability and flexibility of traditional wheeled mobile platforms and footed robotic structures and has enhanced application scenarios and research value. However, the motion control of the two-legged wheeled robot is highly dependent on an accurate dynamics model. At the same time, it has control difficulties such as underdrive, strong coupling, and nonlinearity. These challenges lead to difficulties in achieving effective motion control and self-balancing of the robot. Therefore, proposing an efficient method for the motion control of a two-legged wheeled robot is of great practical significance.Methods This study adopts the idea of a distributed model to establish the dynamics model of the leg-wheel and torso subsystems and address the issue with the huge structure of the overall dynamics model of the two-legged wheeled robot, which is not conducive to characterization and the construction of the controller. These models retain all the dynamics characteristics of the robot and connect them to the inter-module motion/force transfer relationship to complete the whole-body dynamics with the wheel-leg-torso interaction force as the end output force model. Thereafter, the joint moment solver, with the end output force as the task space, is constructed based on this model. It includes feed-forward compensation of the rod inertia force caused by the initial state quantity performed by the observation signal. Then, a distributed control framework with torso position as the task space is proposed to plan the torso joint force and joint moment hierarchically, and the walking motion control architecture based on the whole-body moment is constructed. Based on this walking motion control architecture, an adaptive planning method for the longitudinal trajectory of the torso in jumping motion is proposed, giving the torso the longitudinal velocity required for jumping by planning the longitudinal motion of the torso. To ensure the smoothness of the velocity and acceleration of the jumping motion trajectory, a cubic polynomial is utilized to plan the torso height trajectory of the jumping support phase, the torso height trajectory of the jumping airborne phase is obtained by integrating the velocities, and the variation of its torso height trajectory is presented. Furthermore, the control method of the airborne phase based on the virtual model and the momentum moment theorem is proposed when the torso reaches the jumping speed by controlling the contraction of the legs to detach from the contact between the wheel and the ground and enter into the free-fall state, and the whole jumping process is presented. Finally, the effectiveness of the whole-body moment control system is proved through simulation experiments as well as prototype tests.Results and Discussions A simulation experiment platform is developed using MATLAB to demonstrate the feasibility of the distributed dynamics modeling and whole-body moment control framework for the two-legged wheeled robot. Two walking experiment scenarios, including straight-line and circular motions, are established, along with three jumping simulation experiments at different heights. The velocity following the curve for straight-line motion is shown, with a maximum error of no more than 0.09 m/s. The pitch angle and height following curves of the robot are displayed, indicating height errors ranging from −0.011 m to 0.002 m and pitch angle errors from −0.001 rad to 0.006 rad. For circular motion, the velocity following the curve is displayed with a maximum error of 0.071 m/s. The pitch angle and height following curves for circular motion indicate a maximum height error of 8.633 mm and a maximum pitch angle error of 0.006 rad. The jumping heights are 0.55 m, 0.50 m, and 0.45 m, where the jumping results show a maximum jumping height error of no more than 0.02 m, confirming the feasibility of the distributed dynamics modeling and whole-body moment control framework proposed in this study. A prototype of the two-legged wheeled robot is developed, and multiple motion mode experiments are conducted. The pitch angle and height following curves for the prototype indicate a trunk height error of no more than 3.38 mm and a pitch angle error of no more than 0.04 rad. Finally, by comparing and analyzing the simulation experiment results and prototype experiments, it is found that coordinated wheel and leg movements can achieve higher motion following accuracy while maintaining dynamic balance based on the trunk as the task space. This confirms the correctness of the distributed dynamics modeling and whole-body moment control framework proposed in this study, providing an effective reference for the study of motion control of two-legged wheeled robots.Conclusions This study proposes a distributed whole-body dynamics modeling method to establish the dynamics models of the torso subsystem and the leg-wheel subsystem and realize the complete mapping of the robot’s individual joint moments to the end output force to preserve the dynamic characteristics of the two-legged wheeled robot. A whole-body moment control framework is proposed based on the distributed whole-body dynamics model to achieve motion control and dynamic balance targeting the two-legged wheeled robot with the characteristics of instability, strong coupling, and nonlinearity. A multi-motion mode planning method is proposed based on the whole-body moment control framework to improve the motion performance of the two-legged wheeled robot. Finally, a simulation experiment platform is built to carry out the simulation experiments of jumping and walking motion modes to verify the feasibility of the whole-body moment control system based on the distributed dynamics model. A prototype of a two-legged wheeled robot based on synchronous belt-driven tandem legs and a carbon fiber plate frame is developed and tested in multiple motion modes to prove the correctness of the distributed dynamics model and the whole-body moment control framework of the two-legged wheeled robot. |
| format | Article |
| id | doaj-art-99369cacf40a424aa2a35cf1207a845a |
| institution | DOAJ |
| issn | 2096-3246 |
| language | English |
| publishDate | 2024-09-01 |
| publisher | Editorial Department of Journal of Sichuan University (Engineering Science Edition) |
| record_format | Article |
| series | 工程科学与技术 |
| spelling | doaj-art-99369cacf40a424aa2a35cf1207a845a2025-08-20T02:56:43ZengEditorial Department of Journal of Sichuan University (Engineering Science Edition)工程科学与技术2096-32462024-09-015615616756099176Motion Control Study of Two-legged Wheeled RobotChecao YUXinzhi MAXuejun ZHUXudong YANGHuige LAIAidi YANGObjective The two-legged wheeled robot is a new type of composite ground mobile robot constituted by designing wheels at the end of the legs of footed robots, which combines the improved maneuverability and flexibility of traditional wheeled mobile platforms and footed robotic structures and has enhanced application scenarios and research value. However, the motion control of the two-legged wheeled robot is highly dependent on an accurate dynamics model. At the same time, it has control difficulties such as underdrive, strong coupling, and nonlinearity. These challenges lead to difficulties in achieving effective motion control and self-balancing of the robot. Therefore, proposing an efficient method for the motion control of a two-legged wheeled robot is of great practical significance.Methods This study adopts the idea of a distributed model to establish the dynamics model of the leg-wheel and torso subsystems and address the issue with the huge structure of the overall dynamics model of the two-legged wheeled robot, which is not conducive to characterization and the construction of the controller. These models retain all the dynamics characteristics of the robot and connect them to the inter-module motion/force transfer relationship to complete the whole-body dynamics with the wheel-leg-torso interaction force as the end output force model. Thereafter, the joint moment solver, with the end output force as the task space, is constructed based on this model. It includes feed-forward compensation of the rod inertia force caused by the initial state quantity performed by the observation signal. Then, a distributed control framework with torso position as the task space is proposed to plan the torso joint force and joint moment hierarchically, and the walking motion control architecture based on the whole-body moment is constructed. Based on this walking motion control architecture, an adaptive planning method for the longitudinal trajectory of the torso in jumping motion is proposed, giving the torso the longitudinal velocity required for jumping by planning the longitudinal motion of the torso. To ensure the smoothness of the velocity and acceleration of the jumping motion trajectory, a cubic polynomial is utilized to plan the torso height trajectory of the jumping support phase, the torso height trajectory of the jumping airborne phase is obtained by integrating the velocities, and the variation of its torso height trajectory is presented. Furthermore, the control method of the airborne phase based on the virtual model and the momentum moment theorem is proposed when the torso reaches the jumping speed by controlling the contraction of the legs to detach from the contact between the wheel and the ground and enter into the free-fall state, and the whole jumping process is presented. Finally, the effectiveness of the whole-body moment control system is proved through simulation experiments as well as prototype tests.Results and Discussions A simulation experiment platform is developed using MATLAB to demonstrate the feasibility of the distributed dynamics modeling and whole-body moment control framework for the two-legged wheeled robot. Two walking experiment scenarios, including straight-line and circular motions, are established, along with three jumping simulation experiments at different heights. The velocity following the curve for straight-line motion is shown, with a maximum error of no more than 0.09 m/s. The pitch angle and height following curves of the robot are displayed, indicating height errors ranging from −0.011 m to 0.002 m and pitch angle errors from −0.001 rad to 0.006 rad. For circular motion, the velocity following the curve is displayed with a maximum error of 0.071 m/s. The pitch angle and height following curves for circular motion indicate a maximum height error of 8.633 mm and a maximum pitch angle error of 0.006 rad. The jumping heights are 0.55 m, 0.50 m, and 0.45 m, where the jumping results show a maximum jumping height error of no more than 0.02 m, confirming the feasibility of the distributed dynamics modeling and whole-body moment control framework proposed in this study. A prototype of the two-legged wheeled robot is developed, and multiple motion mode experiments are conducted. The pitch angle and height following curves for the prototype indicate a trunk height error of no more than 3.38 mm and a pitch angle error of no more than 0.04 rad. Finally, by comparing and analyzing the simulation experiment results and prototype experiments, it is found that coordinated wheel and leg movements can achieve higher motion following accuracy while maintaining dynamic balance based on the trunk as the task space. This confirms the correctness of the distributed dynamics modeling and whole-body moment control framework proposed in this study, providing an effective reference for the study of motion control of two-legged wheeled robots.Conclusions This study proposes a distributed whole-body dynamics modeling method to establish the dynamics models of the torso subsystem and the leg-wheel subsystem and realize the complete mapping of the robot’s individual joint moments to the end output force to preserve the dynamic characteristics of the two-legged wheeled robot. A whole-body moment control framework is proposed based on the distributed whole-body dynamics model to achieve motion control and dynamic balance targeting the two-legged wheeled robot with the characteristics of instability, strong coupling, and nonlinearity. A multi-motion mode planning method is proposed based on the whole-body moment control framework to improve the motion performance of the two-legged wheeled robot. Finally, a simulation experiment platform is built to carry out the simulation experiments of jumping and walking motion modes to verify the feasibility of the whole-body moment control system based on the distributed dynamics model. A prototype of a two-legged wheeled robot based on synchronous belt-driven tandem legs and a carbon fiber plate frame is developed and tested in multiple motion modes to prove the correctness of the distributed dynamics model and the whole-body moment control framework of the two-legged wheeled robot.http://jsuese.scu.edu.cn/thesisDetails#10.12454/j.jsuese.202300854Two-legged wheeled robotDistributed modellingTorque controlmotion control |
| spellingShingle | Checao YU Xinzhi MA Xuejun ZHU Xudong YANG Huige LAI Aidi YANG Motion Control Study of Two-legged Wheeled Robot 工程科学与技术 Two-legged wheeled robot Distributed modelling Torque control motion control |
| title | Motion Control Study of Two-legged Wheeled Robot |
| title_full | Motion Control Study of Two-legged Wheeled Robot |
| title_fullStr | Motion Control Study of Two-legged Wheeled Robot |
| title_full_unstemmed | Motion Control Study of Two-legged Wheeled Robot |
| title_short | Motion Control Study of Two-legged Wheeled Robot |
| title_sort | motion control study of two legged wheeled robot |
| topic | Two-legged wheeled robot Distributed modelling Torque control motion control |
| url | http://jsuese.scu.edu.cn/thesisDetails#10.12454/j.jsuese.202300854 |
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