This post, I would like to introduce about the HapticMaster just like a summary about the paper I have read: The HapticMaster, a new high-performance haptic interface
What is the HapticMASTER ?
As you can see from the above picture, the HapticMASTER is a 3 DOF device designed by FCS company and there are 2 dedicated industrial computers for a inner controller and a outer controller. Both of them use VxWorks real-time operating system.
The end effector plate workspace of the HapticMaster spans a 3-dimensional space with a volume of approximately 80 liters. The end plate of the robot arm allows the mounting of difference end effectors.
Controller of HapticMASTER
The HapticMASTER is a force controlled haptic interface:
- Input: force from the human
- Output: the proper displacement
It means when a human pushes the hand, by using the force sensor the device can measure an exact force, therefore give the proper displacement. So simply called: force in and displacement out. It is a Admittance control.
There are 2 controller which are inner servo loop and outer control loop. I just take an explanation from the paper:
The HapticMaster measures the force exerted by the user, preferably measured close to the human hand with a sensitive force sensor. An internal model then calculates the Position, Velocity, and Acceleration (PVA), which a (virtual) object touched in space would get as a result of this force. The PVA-vector is commanded to the robot, which then makes the movement by means of a conventional control law. The general control algorithm is illustrated in Fig. 2. The internal model will typically contain a certain mass, to avoid commanding infinite accelerations. The inner servo loop will cancel the real mass and friction of the mechanical device.
An other interesting thing is two loops of the controllers run at a fixed update rate of 2500 Hz, which is approximately ten times higher than the maximal human discrepance value [Burdea, 1996].
There are some examples people in some laboratories did with HapticMaster:
