What is the three-arm pendulum?

The three-arm pendulum is used for practical implementation and scientific investigation of control concepts and as a laboratory experiment in teaching.

The three-arm pendulum is an experimental setup with a linearly movable carriage or slide on which up to three freely swinging pendulum arms can be mounted. The objectives that can be impressively demonstrated with the aid of the three-arm pendulum include reaching one of the unstable rest positions of the pendulum and quickly approaching the stable rest position. For this purpose, the only manipulated variables available are the travel speed of the carriage and, as measured variables, the carriage position and the arm angles. Core tasks of the three-arm pendulum are:

  • analytical and experimental system modeling
  • design of state controllers for non-linear systems
  • observer design
  • trajectory drive

The high manufacturing quality and the selection of high-quality components of the three-arm pendulum ensure that the highly dynamic setup meets the high demands on the mechanics, the sensors and actuators as well as the computer technology. The three-arm pendulum is characterized by precise travel, minimal backlash and very low slip of the moving components.

The pendulum is controlled via the real-time capable development system dSPACE MicroLabBox, which comes with the associated Matlab/Simulink toolbox for developing the software.

What is the mechanical structure of the three-arm pendulum?

mechanischer  Aufbau Drearm-Pendel
  • Sturdy construction 4650mm (length) x 1360mm (height) x 530 mm (frame dimensions)
  • Aluminum profiles with granite support
  • Required installation space 4750mm x 2600mm x 710mm
  • Linear rail with a travel of approx. 1600 mm
  • Trolley with coupling to the pendulum
  • Weight approx. 130 kg

Which electronics is the three-arm pendulum equipped with?

  • Servocontroller, power supply, mains filter, logic operations, and signal adaptation for connection to dSPACE MicroLabBox in the control cabinet (adaptation to other control is possible)
  • Maximum motion is electrically limited by safety limit switches even in the event of software or inverter errors, and secured by shock absorbers.
  • Error memory and cycle monitoring of the higher-level control by hardware with forced shutdown
  • Drive of the carriage by a servo motor (of approx. 1 kW). The carriage position is measured by a sensor on the axis of the motor with 1024 pulses/revolution (70 mm travel)
  • Power supply of the pendulum arms by accumulators/ and (charging by supplied charger)
  • Resolution of the pendulum axes 2048 pulses per revolution
  • Serial IR data transmission through the hollow shafts of carriage and arm 1
  • Reference switch for detection of absolute carriage position for defined starting point of experiment
  • Limit switch for maximum travel

Do you already know the newsletter of HASOMED GmbH? Here you will receive all information about updates, product enhancements as well as current offers and dates.

Where is the three-arm pendulum used?

The following institutions work with the three-arm pendulum:

  • Max Planck Institute Magdeburg
  • Max Planck Institute Stuttgart
  • University of Magdeburg
  • University of Karlsruhe
  • University of the Federal Armed Forces Hamburg
  • University of the Federal Armed Forces Munich
  • Vienna University of Technology
  • Technical University Ilmenau

In order to promote the exchange of experiences, some users have provided their communication data. You can find them in the following pdf document.

  • three-arm pendulum

    Overview of the institutions

What is included in the scope of delivery of a three-arm pendulum?

  • single pendulum (length 800 mm) as A1 round rod (other lengths are possible on request)
  • first pendulum arm with a center distance of 320 mm
  • second pendulum arm with a center distance of 420 mm
  • third pendulum arm with a length of 450 mm

For further information about the three-arm pendulum, please contact the support of HASOMED Head Office.