PDEng in Robotics: Control of an Archimedes Drive based actuator for wearable robotics

The Professional Doctorate in Engineering (PDEng) programme Robotics offers a 2-year position combining post MSc education and a design project to be carried out at Innovative Mechatronic Systems in Delft. The educational programme, carried out at the University of Twente, will have an in-depth and broadening character with ample attention for professional development and will be partly tailored to the design project. In collaboration with Innovative Mechatronic Systems you will work on high level, creative new designs for complex issues.

The assignment is the design and evaluation of controller of an actuator that is using a traction based gear system invented by IMsystems and will be used in wearable robotics, like exoskeletons and prosthesis.

The wearable robotics research program is funded by NWO-TTW and a cooperation between The University of Twente, the Delft University of Technology, the Eindhoven University of Technology, the Vrije Universiteit Amsterdam and the Radboud University Medical Center.

Within the actuation project of the program, the department of Biomechanical Engineering University of Twente (BE), the Electronic and Mechanical support Division of the Delft University of Technology, production company Hankamp Gears and the traction gear development company Innovative Mechatronic Systems are the major parties.

The aim of the actuator project is to develop an all in one actuator, using the Archimedes Drive as its speed reducer. Because of its low power loss, and true zero backlash, improved performance with respect to the first version with a more traditional type of gear is expected. To be able to implement the new actuator in wearable robotics, new methods to control a traction based system need to be developed.

The Archimedes Drive is a compound planetary traction drive, that uses traction between steel rollers to transmit the torque (instead of gear teeth). Besides the obvious advantages, such as zero backlash and low friction, there is the introduction of a new property: Kinematic creep. That is the torque and velocity dependent micro slip at the traction surface. It is our belief that this unique property can be an advantage for good torque control, better admittance control and/or improved controlled transparency.

The challenge is to develop control methods to benefit the most from this novel type of actuator. Therefore, identification of all properties of an Archimedes Drive, and methods to model (analytically and discrete) the system will be the start of this assignment. When the system is well known, new stable (nonlinear) control methods should be designed These low-level controllers should enable the integrators of the actuator in wearable systems, to implement the control of their wearable devices.