| Compared with traditional mobile robots,hopping robots can move on discontinuous surfaces,which is one of the important ways to overcome complex terrain.Small hopping robots with small volume,light weight and large hopping height can better adapt to complex enviro N·ments,effectively use small area footholds,and complete tasks such as exploration.However,most of the existing small hopping robots can only perform intermittent hopping,which is difficult to apply in practice.It is urgent to study a type of robot that can continuously hop,and to study the algorithm of its landing position control,so that it can meet the needs of actual use.Starting from the continuous motion point position control that restricts the application of the hopping robot,the hopping robot is simplified to a mass spring inverted pendulum model,and the variables required to control the robot's point position are determined as relative leg length,attitude angle and speed,where the speed error is The main factor of the drop point error.The overall mechanism of the robot is designed.A gear-link mechanism driven by a series elastic actuator is used to achieve hopping motion.A DC brush motor is used to drive the mass of the robot's tail to achieve attitude control.Based on the Lagrangian method and the principle of conservation of impulse,the dynamic model of the ground contact process of the hopping mechanism is established,and the dynamic model of attitude control is established based on the principle of conservation of angular momentum.A robot control system is developed.The encoder realizes the leg rotation detection,the attitude detection chip realizes the pitch and roll angle detection,and combines with the ground contact dynamics model to realize the closed-loop control of the robot's movement speed.The principle prototype of a single-degree-of-freedom continuous hopping robot is developed.The principle prototype adopts an embedded system,and its hardware core is a six-phase full-bridge brushless motor drive circuit controlled by STM32.The brushless DC motor drive algorithm and the air leg angle control algorithm with mixed force and position are designed,and carried out the vertical take-off and ground touchdown experiments.The results showed that the experiment obtained the law of the change of the leg rotation angle and the dynamic model prediction during the robot touchdown process Consistent.A discrete control algorithm based on prediction of the rotation angle is designed,and a continuous hopping of 250 mm along the guide rail of the prototype is realized by using this algorithm.In order to realize the robot attitude control,the embedded system hardware is designed,the body attitude is calculated based on the quaternion method,and the accelerometer information is complementary filtered,the robot air active attitude control algorithm is designed,and the air active attitude control experiment is carried out to verify The feasibility of the attitude control scheme,the final control angle error is less than 2°.The ground-touching experiments of the robot under different generalized conditions have been carried out to verify the accuracy of the attitude angle and velocity changes predicted by the non-active attitude control,that is,the ground-touching dynamics model.In order to realize the continuous motion of the robot and meet the control requirements of the landing position,a deadbeat speed control strategy based on the ground contact dynamics model is designed.A joint simulation model of the hopping mechanism and the attitude control mechanism is established.The third-order Taylor expansion is used to fit the selected touchdown simulation results,and the deadbeat control function is obtained,and the discrete velocity sampling algorithm and disturbance compensation algorithm are designed.A continuous hopping simulation is carried out,and the results show that the error of the first three landing points is within 50 mm,which proves that the landing point control method is feasible. |
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