In context
Space deployable mechanisms, such as antennas and solar arrays, are designed for low-gravity orbit conditions, making ground testing challenging due to gravity. Traditional unloading methods like suspension and air-floating have limitations in certain configurations, prompting the need for more flexible solutions.
What was reported
Researchers proposed a gravity unloading method using robot force/position control, where an industrial robot applies a lifting force to balance the gravity of deployable components while following their deployment trajectory. The method combines position control for coarse tracking and force control for precise adjustment, enabling stable unloading throughout the entire deployment process.
For a specific antenna deployment test, the study provided calculation methods for position and force control adjustments, including a lifting force calculation when the lifting point does not coincide with the center of gravity, and an online identification method for mass characteristics when unknown. A tangential force-based recognition method was also developed to determine the start and stop timing of the robot's following motion.
In experiments, a 6-DOF industrial robot unloaded a simulated component with a gravity torque of 153 N·m, driven by a servo motor rated at 2.39 N·m. After a deployment angle of 10°, the maximum lifting force prediction error was within 1.3 N, and the joint torque remained within the motor's rated range throughout the deployment.
Why it mattered
This method offers a flexible, compact alternative to traditional gravity unloading systems, enabling rapid setup for specific applications and expanding the use of standard industrial robots in aerospace ground testing.
“The gravity unloading for the entire deployment process is achieved, ensuring that the joint torque remains within the rated torque range of the motor in the entire deployment process.”
Source: 《机器人》期刊 (robot.sia.cn) · Published 2025-03-15 · “基于机器人力/位控制的空间可展开机构地面重力卸载”