C11 - SCARA Robot

Benchmark C11 SCARA Robot investigates movement and control of SCARA robot (Selective Compliance Assembly Robot Arm).

This robot type has two vertical revolute joints and one vertical prismatic joint. The axes of all three joints are vertical. The equations of motion follow the typical implicit form: mass matrix times accelerations equal to generalized forces. A DC-motor (ODE model with current limitations) with PD-control drives the specific movement of the robot (point-to-point control).

Challenge for implementation is the implicit model description, whereby handling requires a-priori manual resolving to an explicit state space, or numerical resolving in implementation, or use of a DAE-solver; solution may also make use of physical modelling approaches which decrease the modelling effort, but which need special care for in case of state-dependent changes.

As further challenge, the benchmark requires modelling and implementation of a collision avoidance – which requires state event handling and model change (depending on implementation).

The educational aspects of this benchmark are multifaceted: an introduction to robot modelling and control, a guideline for implementing implicit models and state event handling, and a test for the capabilities of physical modelling environments as Modelica, and some more. Interestingly, also spreadsheet calculation allows an implementation of this comparison.