The mechanics of the DLR Force Feedback Joystick consists of a cardanic joint solution which is driven by two brushed DC motors over cable gears. The solution enables a working space on both axes of ± 20° and forces on the handle up to 10N.
The quality of the used actuators, the high resolution of the position measuring system (optical encoders coupled on the motor shaft) and the interface to the control board allows a high bandwidth (up to 5 kHz) of force feedback.
The control algorithms are implemented on a PC based DSP board DS1102 from dSpace using Texas Instruments TMS 320C31 Signal Processor. In this version, the communication between the host PC and the DSP board is done using a dual port memory. For the control software development all the dSpace software prototyping tools can be used.
Since the used gears have no backlash and very small friction the exerted force is proportional to the current command. To verify this issue, a precise force calibration is done for every joystick hardware.