We have developed a new robot arm with six joints that have torque sensors and geared reduction systems. This arm has compliance control ability without using a wrist force sensor. The techniques adopted here are the low friction and low gear ratio reduction system, nonlinear torque compensation, inertial torque feedforward compensation and joint torque control using joint torque sensor feedback. The experimental results show that this robot has high accuracy of trajectory in spite of large compliance, i.e. low position feedback gains. This robot can also take practical industrial tasks in high speed under uncertain positioning of works.

Numerous issues remain to be solved in improving the efficiency of the complex assembly processes existing in the automobile chassis and drive train system assembling plants due to their being labor intensive and their reliance on the dexterity of human operators. Equally important, factors such as labor shortages and reduced work hours are expected to become more of an issue in the coming years. It is extremely important, therefore, to address the qualitative and quantitative issues of labor in the design and manufacturing aspects of the assembly line, as well as the issue of the assembly operators themselves. To address these issues, we have developed and put into practical use a multi-arm type assembly robot capable of handling complex and both-hands assembly operations. In this paper, we present its development concept, performance, and examples of actual applications.