Research On Dynamic Characteristic Of A One-legged Hopping Robot Based On Pneumatically Actuated Leg In Vertical Direction

One-legged hopping robot involves pneumatic and hydraulic servo system,dynamics of multi-body system, self-balancing control and other multi-disciplinarybasic theory and key technology, these researches lay a good foundation formulti-legged walking robot. One-legged hopping robot is this report’s researchsubject, and it is focused on dynamic characteristics and controlling algorithm usedin robot’s continuous and stable hopping.The hopping cycle is divided to compression period, extension period and flightperiod on the basis of hopping process, extension period contains thrust period anddecompression period. For the different requirements of compression distance andtime, control algorithms based on closed and opening system of compression periodare proposed. For the complexity of extension, energy supplement is carried on in thethrust period, upper and lower valves are closed in the decompression period, and therobot can lift off the ground by the gas pressure difference between the upper andlower chamber, and the algorithm can avoid striking between the piston and chamber,reducing the system’s shock. For the control requirement of the flight period, analgorithm is proposed based on the gas internal energy, and the control algorithm isused to control the gas pressure and the piston position. Every period of the robot’smathematical model is established, including the cylinder kinetic equations, theopening and closed systems of energy, flow, temperature and friction equations. Theequation of the control algorithm, servo proportional valve’s dynamics and controlequation are also established.Every period’s simulation models are established through the MATLABSIMULINK module based on the math model, and every period of the hopping cycleis detailedly analyzed. In the compression period, the influence curve of differentvalve’s opening time on the characteristics of compression period is got fromcomparative analysis of closed and opening compression system’s influence oncompression distance and time. In the extension period, influence analysis ofdifferent thrust period and method on the robot’s characteristic are carried out,achieving the robot’s height regulation. In the flight period, effectiveness of thealgorithm that used gas internal energy to control gas pressure and piston position isproved. And then, Co-simulation models are established, the robot’s dynamicscharacteristics of the whole process is analyzed, Simulation results prove that stablehopping and controllable hopping can be achieved using the proposed algorithms. Using C8051F120MCU as the robot’s controller, containing one-legged hoppingrobot, proportional flow valves, pressure sensors, positon sensor and filter amplifiercircuit, the one-legged vertical hopping robot platform is constructed. And then stablehopping control algorithm of the robot and data transmission program areprogrammed, stable hopping experiments are carried out in the experimental platform,achieving the robot’s continuous and stable hopping.