Rotary Flexible Joint

This laboratory experiment is suitable for modeling the dynamic behavior of large robot arms with flexible joints. The following questions, among others, arise during the controller design for this system: How fast can the arm be brought into the target position? Is overshooting allowed (precision)? Are there acceleration limits that must not be exceeded? Does the mass of the object to be transported vary?

The Setup

The experimental setup consists of three main parts:

  1. base module
  2. joint module
  3. arm

The base module includes a DC motor that rotates the joint module via a gearbox. The arm is flexibly mounted on the joint module with springs. The angle between the joint module and the arm, which is required for control, is measured by a sensor. The system's behavior can be modified by different spring positions, arm lengths and masses.

Videos: Example Rotation of the Arm to a new Target Position

In the first video you can see how the arm is rotated to a new target position without control. The arm clearly overshoots and takes time to stand still, a undesirable behaviour in practical applications.

In the second video, a control concept is applied yielding an obvious improvement. The arm now reaches the target position almost without overshooting and stops moving immediately.

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First Video: Rotary Flexible Joint (without control)

After activation, data may be transmitted to third parties. Data protection declaration., opens in new window

Second Video: Rotary Flexible Joint (with a control concept)

Challenges for Teaching

  • Mathematical modeling of the system, parameter identification
  • Design of different control concepts (state space control, flatness-based feedforward control, 2-degree-of-freedom control, model predictive control)
  • Investigation of the impact of model-plant mismatch
  • Investigation of the influence of disturbances

Application in Practice

  • Control of robot arms

Courses

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