Development of a Direct-Drive Servomechanism for Use in Robots with Six Degrees of Freedom and Consisting of Servo Actuators Using Metal Hydrides

该关节结构由N个平移驱动器组成的组合系统组成。根据关节静力学仿真结果确定了N的数量：在评估时考虑了结构的简单性和运动区域的宽度，然后明确了要获得6个自由度的运动需要n=6以上，并且N=6和N=8在宽度和可控性上没有什么不同。因此，在这种情况下选择N=6，已经成功完成了关于关节运动动力学的两个重要软件系统，以通过给出每个致动器的长度来计算关节位置和方向，反之亦然。虽然该关节结构中需要采用MH（金属氢化物）作动器，但实际上本研究中采用的是气动作动器。1988年的另一份报告中已经说明了原因。控制系统由计算机PID控制器和PWM电路构成。通过信号处理和物理定律确定了执行器的精确数学模型。对该6自由度关节进行了位置控制。结果表明：（1）虽然各执行器之间的相互干扰影响不小，但对各自由度的控制都是准确的，其响应时间约为1秒。（2）在PID控制器中引入I元件，减小了超调量，改善了控制特性，减小了执行器间干扰的影响，并对非线性元件的影响进行补偿，是本课题今后研究的方向。

The joint structure consists of an assembled system by N actuators in translation. The number N has been determined according to the simulation results on joint statics: The simplicity of structure and the width of moving area are considered in evaluating it. Then, it has been made clear that more than n=6 are necessary for getting the movememnts of 6 degrees of freedom and that there is nothing different between N=6 and N=8 in the width and the controllability. So, N=6 was selected in this case the two important software systems on the dynamics of joint movement have been successfully completed to calculate joint positions and orientations by giving the lengths of each actuators and vice versa. These are useful in designing the controller.Though MH(Metal Hydride) actuators should be used in this joint structure, penumatic actuators have been used in this study practically. The reasons were already written in another report of 1988. The control system has been constructed by a computer based PID controller and a PWM circuit. The accurate mathematical model of actuators was determined by the signal processing and the law of physics. The position control has been done to this joint of 6 degrees of freedom. The results are as follows:(1)though the effects of mutual interference were not small between each actuators, the control for every degrees of freedom was accurate and its response time was about 1 second.(2)The wind-up of I element in the PID controller made the over-shoot decrease and then improved control characteristics.The future problems at control in this study are to decrease effects of the interference between actuators and to compensate effects of non-linear elements.