Lightweight space robot with precise control developed

The Beijing Institute of Technology.

The proposed method of admittance control has better performance than the traditional method. Space, science and technology.

There are machines in space. The ideal candidates for space exploration are the landers on the moon and the rovers on Mars, they can bear extreme environments while consistently repeating the same tasks in exactly the same way. They can do both dangerous and mundane jobs, like space walks and polishing a spacecraft's surface. With space missions increasing in number and requiring more equipment, there's a need for a lightweight robotic arm that can manipulate in environments difficult for humans.

The control schemes that can move such arms on Earth, where the planes of operation are flat, do not translate to space, where the environment is unpredictable and changeable. The researchers at the School of Mechanical Engineering and Automation at the Harbin Institute of Technology have developed a robotic arm that can carry almost a quarter of its own weight.

The results were published in Space: Science & Technology.

"In order to solve the problems of strict restrictions on the mass and size of the manipulator, as well as the high requirements for reliability and safety of the control method in space operation, we developed a light space manipulator and proposed a new control method," said the author.

When in operation, the manipulator needs to exert constant force control.

For a curved surface in an unknown environment, the traditional method of constant force control would fail because the normal force is often changed in real time. In order to overcome this difficulty, we propose an adaptive admittance control that can realize real-time correction of the desired position of the end of the manipulator so that it is in full contact and realizes constant force control.

Compare it to a drawing on paper. It's easier to maintain even pressure when the paper is on a flat desktop. 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 how much pressure to exert based on the position of the pen and the ball.

The researchers imposed a control method that removes the need for steady-state correction to keep the force control constant. When the environment is predictable, steady-state correction applies the potential error to the full movement. If the desk's surface is rough and strong, the pressure of the pen can be lightened to maintain a constant line. Keeping a constant corrective state results in more errors since not all corrections apply to all errors.

The control method for the lightweight manipulator was tested and found to be more stable than a traditional control method, and that the mechanical arm could adjust quicker than a traditionally controlled manipulator.

The proposed light space manipulator and the integral adaptive admittance control method can solve practical problems on on-orbit servicing, such as space target capturing, on-orbital assemble, and so on.

The control approach can be applied to themachining process of robotic surface grinder and polishers, and the work can serve as a reference for the design of light manipulators in the future.

A Light Space Manipulator with High Load-to-Weight Ratio: System Development and Compliance Control is a paper by Zhiwei Wu and his colleagues. The DOI is 10.4133/2021.

The Beijing Institute of Technology provided this.

The lightweight space robot with precise control was retrieved from on December 3, 2021.

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