Research About Gait Planning And Balance Control Of Quadruped Robot

Quadruped walking robot is an important branch of robot. Quadruped walkingrobot not only has heave loading capacity, but also adapts to the all-terrain variety moreeasily. It could not only move slowly and smoothly with statically stable gait, but alsorun with dynamically stable gait. If installed with a manipulator, it will become a sta-ble and flexible working platform while standing. Therefore, quadruped walking robotcould be one of the first practical physical types. On the study of quadruped walk-ing robot, gait planning and balance control of quadruped robot is the subject withgreat significance. In order to improve speed of travel and energy efficiency effec-tively, and enhance the ability of adapting the rough terrain during walking, we takethe quadrupedal walking robot AIBO as research platform and study motion control ofquadrupedal legged robot in the following three aspects:1. The gait planning and optimization of quadruped robotThe most common method of gait planning of quadruped robots is the controlmethod based on the kinematic model. Experimental results show that the planning tra-jectory using this method is not identical with the actual trajectory of locomotion. Thisproblem causes that the robot can not move following the preliminary mode designedexactly. Therefore, this paper presents a gait control method using ZMP (zero-momentpoint) trajectory planning by studying the body sway phenomenon of robots duringwalking, which introduces the dynamic planning based on the the control method ofthe kinematic model: control the body posture during walking to change the supportpolygon formed by the robot foot and the ground, and in the mean time use ZMPtrajectory planning to generate the foot trajectory during stance phase. This methoduses the model-based gait control method effectively, thus reduces the computationalcomplexity of totally using dynamic planning method, and satisfies the need of real-time algorithm. Since the designed controller contains a large number of parameters,we also use an evolutionary learning method based on genetic algorithm to optimizethose gait control parameters. Since we effectively use the gait parameters based on thekinematic planning to initialize generation, the algorithm constringency is much better.Moreover, we take full account of the stability factor when choosing the fitness func-tion, the stability of the optimal gait is improved. In the experiments, the AIBO robotcan obtain the optimal gait autonomously, and its maximum speed achieves 455 mm/s with stability. The experimental results show that the robots can obtain the optimal gaitwith better stability and stronger adaptability to uneven terrain by using the proposedgait control method.2. The balance control and optimization of quadruped robotConcentrated on the danger of turnover imposed by sudden external shocks ofrobots during normal walking, scientists in various countries devote their lives to propos-ing different"reference point"which could be used as the stability criteria of walkingrobot. Most results are carried out with simulation experiments using simulated robots,which can prove the validity of related theory. However, for the entity robot, due to allkinds of errors and noises caused by sensors themselves, the robots can't tell exactlythe outer world and finally obtain the accurate information of their status. Therefore,for physical robot, this paper introduces a linear regress model to predict the conditionof being turnover effectively, which improves the precision and accuracy of robot statedetection. On this basis, we present a balance control method based on the orbital en-ergy model to achieve stand-restoration after turnover, using both attitude control and"taking a step"strategy to achieve balance control. Here we use an of?ine supervisedlearning method to optimize the theoretic foothold model. In the experiment of AIBOrobots, this method reduces the frequency of turnover by more than half, accordinglyproving its validity and feasibility.3. The motion control system of quadruped walking robotQuadruped walking robot needs to achieve fast lineal locomotion, well turning andemergency braking; when the robot loses its balance in emergency, it needs to determinewhether the body will be in the danger of turnover, then could recover itself automati-cally; when the robot turns over unfortunately, it needs to achieve fast stand-restorationafter turnover; when it becomes a working platform, it needs to carry out various taskssuch as griping objects through controlling whole-body movement. Therefore, a com-plete motion control system is designed based on the actual application requirementsof quadrupedal walking robot. Each layer has clearly defined duties and specific re-quirements, and also mutually related and restraint, which will effectively coordinateall kinds of motion behaviors, and satisfy various application requirements.Summary and some open problems that require further investigation are given inChapter 6.