## 1 Introduction
In order to achieve the research goal, this study drew the following results: (1) A dynamic based optimization problem was formulated in which motion profiles defined over a fixed cycle time are used as optimization variables and the AM-GM ratio of the acceleration factors of each joint is used as an objective function. (2) For a given initial and final pose of a robot, a global minimum solution that that makes the accelerated life test times for the drive components of all joints of a robot equal was derived. (3) Using the kinematics and dynamics parameters of an actual 6-DoF industrial robot, a global optimal solution was obtained for various cycle times and it was confirmed that the acceleration factor is inversely proportional to the cycle time. From the above results, it was possible to design robot motions which have the following useful properties for system-level life test: equal test time for the drive components of all joints of a robot, smooth joint displacement so that the required joint torque is continuous, and high acceleration factor to shorten the required test time. Robotic motion optimizations for various robots have been studied to date [4; 5; 6; 7; 8; 9; 10], but most have focused on optimizing efficiency and performance, such as minimizing energy consumption or shortening cycle time to perform a particular task. What distinguishes the present study from past works relating the robot motion optimization is that the present study is a result of studies on motion optimization to ensure that the load applied to each drive component is evenly distributed. In refs. [4; 5; 6; 7; 8], motion optimization problems are established with robot dynamics based on Lie group. A recursive algorithm to obtain the analytic gradient that can be used to perform motion optimization is presented, and the displacement of the robot joint was parameterized with a B-spline curve to convert the problem into a finite-dimensional constrained optimization problem. In [PERSON] et al. [6] and [PERSON] et al. [7], minimum effort optimal motions for various open chain manipulators are examined, In [PERSON] el al. [8], the result of applying motion optimization for maximizing payloadto the industrial robot PUMA is presented. The result of applying motion optimization technique to the hydraulic excavator and the bipedal humanoid robot are given in [9] and [10], respectively. The efficient generation of the natural robot motion based on dynamics-based optimization and principal component analysis is presented in [11]. Studies on the reliability and lifetime of robots have been conducted mainly on a component-by-component basis, and there have been few studies to systematically design the life test at system-level. In this paper, it was attempted to design robot motions for the accelerated life test of drive components at system level by applying a robot motion optimization technique. Studies on the reliability and lifetime of precision gearboxes used in robots are presented in [12; 13; 14] and work on servo motors are summarized in [15]. In ref. [16], an accelerated life test was performed on individual components to calculate the reliability of the entire system from the reliability of each component of the robot, and the average lifetime of the system was estimated from the results. In ref. [17], a study on motion optimization to increase the service life of the robot gearbox was conducted. This paper is configured as follows. In Section 2, modeling for the dynamic analysis of industrial 6-DoF is presented. Section 3 introduces a concept of a zero failure life test and an acceleration factor in relation to an accelerated life test for drive components of an industrial 6-DoF robot. Section 4 establishes a motion optimization problem that can verify the lifetime of all the drive components within the zero failure test time by matching the acceleration factor of each robot joint equally. Section 5 shows the results of performing the motion profile optimization to the actual 6-DoF industrial robot.