The application in the ROKVISS ground station demands a very accurate force display of the contact forces measured in the remote environment, enabling in this way the detection of quality distinctions of different surface conditionings with coating materials in space environments.
For this purpose the friction in the mechanics of the DLR force feedback joystick was reduced by inserting ball bearings in every axe carrier as well as some changes in the gear reduction ratio and the current control of both motors.
The structure of the control electronics could be significantly simplified by the usage of a Freescale DSP Controller from the 56F8XX family. The new electronic design allows to interface brushed and brushless DC motors.
For communication with the on ground computer the joystick was equipped with a USB interface. To achieve a communication bandwidth of 1 kHz, a special USB interface chip was needed. The standard USB peripheral interfaces for force feedback joysticks enhance only refreshing rates bigger then 10ms.
For this application we developed a USB driver for the real time operating system.
In the handle of the joystick we inserted a digital joystick, which can be used for the passive position steering of the robot or to move the pan-tilt unit of a camera.