Research On Dynamic Characteristics Of Vertical Hopping Of Pneumatic One-legged Robot

Small area support, crossover stride, cross obstacle by hopping are typical of the walking robot. Therefore, it has advantages in the fields, hill, rubble and battlefield. In the process of walking, the support constraint of the ground and the gravity of the robot always change. As a result, the walking robot is in static instablility states. Particularly, stability of the one-legged robot is the worst. It has great theoretical and practical significance to study the hopping ability and movement stablility of the one-legged robot.The key technologies of the one-legged robot include the hopping drive strategies, the body attitude detection and adjustment technology. Specifically speaking, the hopping drive strategies include the buffer capacity and explosive force. The one-legged robot is consisted of body, pneumatic leg and a ball joint. The body and the leg are bolted together by the ball joint. Therefore, the leg can swing based on the body. The swing is drived by two hydraulic cylinders. The connection joints between the hydraulic cylinder and the body or the leg are discussed. Based on the geometrical properties of the characteristic points, the space geometry and vector algebra theory, the kinematic inverse solution and forward solution of the attitude adjustment mechanism are deduced. By four ultrasonic sensors, the body attitude detection system is designed. The validity of the kinematic solution is vefified by MATLAB and SOLIDWORKS.By virtue of dynamics, thermodynamics and automatic control theory, the pneumatic servo system which is based on the energy control algorithm is built. By analysis of the motion law of the piston position and action law of the air, the kinetic equations, energy equations, gasflow equations, temperature equations and friction force equations are established. And the pneumatic servo control which is based on the energy control algorithm is proposed. A pneumatic position servo model of the pneumatic acutuated leg at the flight phase is developed by MATLAB.Based on the dynamics, collision theory, automation control theory and the research results of the pneumatic servo system, the comprehensive dynamic model is established. The model includes the mathematic models of landing collision, touchdown phase, shock of take-off and motion of flight phase. A dynamic simulation model of a hopping cycle of the one-legged robot is built in MATLAB. Applying the simulation model, the movement process of the vertical hopping of the robot and the variation law of the dynamic parameters are simulated. The simulation results validate the effectiveness of the mathematic model. Influential factors on the hopping height include: hopping height of the last cycle, preset values of the piston position and chambers pressure, the start charging threshold of the upper chamber pressure at the touchdown phase, the stop charging threshold of the piston position and the effective area of the throttle orifice. In view of the above factors, a simulation study is carried out. Both the usable range and the better range of the factors are obtained. In addition, the effects of the preset value of lower chamber pressure and piston position and the stop charging threshold of the piston position on the landing collision and shock of take-off are simulated. Both the usable range and the better range of the factors are obtained. The above results lay the foundation for the stable vertical hopping of the one-legged robot.The experimental platform is consisted of DSP control system, multi-sensors detection system, pneumatic servo system and mechanical system. The experiments of control precision of the piston position during the flight phase, dynamic characteristic and the stability of the vertical hopping of the robot are performed. Influencing rules of the preset value of the lower chamber pressure and piston position, start time and duration of the charging stage, effective area of the throttle orifice on the hopping height are studied. In addition, Influencing rules of the preset value of the lower chamber pressure and piston position and duration of the charging stage on the landing collision and shock of take-off are also studied. By comparison with the simulation results, the validity of the dynamic models of the pneumatic servo system, the vertical hopping and the simulation results are demonstrated.Dynamic models of the kinematics, the body attitude detection and adjustment system, pneumatic servo system and continuously vertical hopping of the robot are established. Based on the models, simulations and experiment researches are carried out. Theoretical analysis of the body attitude detection and adjustment system are given and verified. Both vertical hopping of the stable height and vertical hopping of the changeable height are realized in theory and experiment.