| Exoskeleton robot technology began in the military field, which wasoriginally designed to amplify the power of the soldiers and enhance theirendurance, it reflects a long-standing desire of mankind, that is, throughmachine to amplify the power of the human limb, and keep the body’s flexible.In recent years, it began to extend into civilian areas, the most notableapplication is helping the people whose lower limb is weak or paralyzed getrid of wheelchairs and stand and walk like a normal person. All the bodymovements are controlled by the nervous system, and the strength is relatedwith human muscle, when people gradually aging or encounter an accidentwhich make one can not move like a normal man. Lower extremityexoskeleton will give a certain power to assist human make some motions, sothat the human body’s own consumption is reduced. As walking motion is oneof the most complex and the most common movement, if the people can relyon the exoskeleton device to stand up and walk instead of wheelchair, it willhave a tremendous positive impact on their attitude towards their life. Lower extremity exoskeleton system is a man-machine integration devicewhich is worn on the lower extremities of the body. It combines the controltechnology, ergonomics, robotics, bionics, signal processing technology,sensor technology and so on. It emphasizes the human-machine’s combination,and realize complementary of the the body’s control and machine’s forces. Thelower extremity exoskeleton‘s development will have very broad applicationprospects in many field which include individual combat equipment,rehabilitation equipment, heavy and hazardous labor improvement equipment,and the new environmental walking equipment.This paper analyzes the structure and freedom of the human lower limb,human walking mechanism and kinematics, then designed a virtual prototypeof lower extremity exoskeleton robot. According to specific controlrequirements, this paper designed a differential gear train drives which isinnovative, and designed a walking stick with trigger device. Then designlower extremity exoskeleton’s control system, because the target population ofthis article is the people whose lower limb is weak or paralyzed, the mainfunction is allowing users to standing and walking, so it must use passivecontrol systems, lower extremity exoskeleton walking control is controlled bythe human upper limb and crutches, human lower limb is passive whosemovement is driven entirely by the exoskeleton. According to this requirementwe complete the lower extremity exoskeleton’s design of control system’ssoftware and hardware. Finally, through the theoretical analysis kinematics and dynamics of unilateral lower extremity exoskeleton, we can get its kinematicsand kinetics equation. By kinematic equations we can calculate the pose andposture of the end of the lower extremity exoskeleton relative to the hip joint’scoordinate system through the joint angles. By kinetic equation, we can obtainthe impact of lower extremity exoskeleton’s effective inertia and couplinginertia and gravity on joint drive’s torque. It provides a theoretical basis for theexoskeleton motion control. As the human lower limb exoskeleton should havethe function of walking, so it need track the angular displacement curve of thehuman body’s normal walking. By analyzing the characteristics of the humanbody’s joint angular velocity and power curve, we know that exoskeleton jointhave a character whose speed and power have a wide range of variation. If wechoose a single motor, we should select high-power motor, it will easily lead tolarge inertia, deterioration of dynamic performance. In this paper, by usingdifferential planetary gear mechanism’s characteristics whose two input havedifferent influence on the one output, we designed bangbang-PD trajectorytracking control algorithm. Then through the co-simulation of ADAMS andSIMULINK, confirmed that this paper’s control method has better gaittrajectory tracking performance compared with the traditional control method. |
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