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个平移执行机构组成的装配系统组成。根据节理静力学仿真结果确定了N数：在评价时考虑了结构的简单性和活动区域的宽度。明确了获得6自由度运动需要n=6以上，且N=6和N=8在宽度和可控性上没有区别。因此，在这种情况下，选择N=6，成功地完成了关节运动动力学的两个重要软件系统，通过给出每个执行器的长度来计算关节的位置和方向，反之亦然。虽然在这种连接结构中应该使用金属氢化物(MH)执行器，但在本研究中实际使用的是气动执行器。理由已写在1988年的另一份报告中。控制系统由基于计算机的PID控制器和脉宽调制电路构成。根据信号处理和物理定律，确定了执行器的精确数学模型。对该六自由度关节进行了位置控制。研究结果如下：(1)虽然各执行器之间相互干扰的影响不小，但各自由度的控制精度较高，响应时间约为1秒。(2)在PID控制器中加入I元件使超调量减小，从而改善了控制特性。降低执行器间干扰的影响，补偿非线性元件的影响，是本研究控制中有待解决的问题。

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.