Development of a lightweight space robot with precise control – Eurasia Review
The robots are already in space. From landers on the moon to rovers on Mars and more, robots are the perfect candidates for space exploration: they can endure extreme environments while consistently repeating the same tasks in exactly the same way without tiring. Like robots on Earth, they can perform tasks that are both dangerous and mundane, from spacewalks to polishing the surface of a spaceship. With more and more space missions for scientific purposes, requiring more equipment, there is a need for a lightweight robotic arm that can be handled in harsh environments for humans.
However, the control schemes that can move such arms on Earth, where the plans of operation are flat, do not translate into space, where the environment is unpredictable and changeable. To solve this problem, researchers at the School of Mechanical Engineering and Automation at the Harbin Institute of Technology developed a robotic arm weighing 9.23 kilograms – about the size of a baby from a an – able to carry almost a quarter of its own weight, with the ability to adjust its position and speed in real time according to its surroundings.
They published their results in Space: Science and technology.
“In order to solve the problems of strict restrictions on the mass and size of the manipulator, as well as the high demands on the reliability and safety of the control method in space operations, we have developed a lightweight space manipulator and proposed a new method of control, “said corresponding author Wenfu Xu, professor at the School of Mechanical and Automation Engineering at Harbin Institute of Technology and the State Key Laboratory of Robotics and System.
Such a manipulator must exert constant force control when in operation.
“For the constant force control of an airplane, the direction of the control force is constant, but for a curved surface in an unfamiliar environment, its normal vector is often changed in real time, so the traditional method would fail. “Xu said. âTo overcome this difficulty, we provide full adaptive intake control that can achieve real-time correction of the desired position of the manipulator end so that it is in full contact and achieves constant force control. “
Compare it to a one-line drawing on a piece of paper. When the paper is on a flat desk, it is much easier to maintain even pressure across the entire line. Drawing an identical line on a sheet of paper wrapped around a bouncing ball is much more difficult and requires specific calculations to understand the movement of the ball and the pressure to be exerted depending on the position of the pen and the ball.
To keep the spatial manipulator force control constant, the researchers imposed a control method that eliminates the need for steady-state correction, a key component of control systems in known environments. Steady state correction applies the potential error to full motion, which alleviates problems when the environment is predictable. For example, if the manipulator knows that the surface of the desk is rough and that strong pressure could tear the paper, it can ease the pressure of the pen to maintain a constant line. But when the surface is changeable and unpredictable, maintaining a constant corrective state leads to more errors, because not all corrections apply to all errors.
The researchers tested their control method for the light manipulator and found that, even on an unknown surface, the mechanical arm could adjust faster than a traditionally controlled manipulator, resulting in a tracking effect stable enough for practical applications. .
“The use of the proposed lightweight space manipulator and the integrated adaptive admission control method can solve practical in-orbit maintenance problems, such as space target capture, in-orbit assembly, orbital repair, etc. “Xu said.
According to Xu, this work can serve as a benchmark for the design of lightweight manipulators in the future, while the control approach can be applied to the machining process of robotic grinders and polishers.