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Passive Trajectory Enhancing Robot (PTER) Project Description The device pictured in figure 1 is an existing mechanism called PTER (Passive Trajectory Enhancing Robot) that is a Haptic Robot. Another way of thinking of PTER is as a super joystick that is used to operate another robot or simulate a programmed virtual reality environment. PTER resists the humans motion in certain directions, simulating barriers or constraints on where the joystick can be moved based on feedback from the teleoperated robot or programmed virtual reality. One important property of PTER is that it is a Passive Haptic Robot and can not use motors to simulate these barriers or constraints, but can only resist motion in the unwanted directions by redirecting or dissipating energy through clutches, brakes, or continuously variable transmissions.
Figure 1 Current Configuration Presently PTER utilizes electromechanical friction brakes / clutches to couple link 1 to the base (brake I), link 2 to the base (II), links 1 and 2 directly (brake III), and links 1 and 2 inversely (as link 1 moves clockwise link 2 moves counter clockwise and visa versa) (brake IV). (See figure 1 through 3). As can be seen in the present configuration, the brakes are directly connected to the links and never make a full revolution. The brakes / clutches turn at erratic slow speeds, often switching directions. Figure 2
Figure 3 New Clutch Requirements We are looking for clutches / brakes to replace the existing hardware. The new clutches / brakes are to be controlled through a computer and should be able to resist slippage for an applied torque of around 50 N-M. These brakes / clutches must provide controlled slippage and torque transmission between the links they are coupling, while exhibiting smooth, quick response to new slippage and torque requirements determined by the computer. Modification to PTER can be made to accommodate mounting constraints of the new clutches. It might also be possible to no longer mount the clutches directly to the links, but fabricate a mechanism that couples the clutches to the link through a gear reduction, allowing remote mounting of the clutches. This may also decrease the torque requirements and increase the number of revolutions the clutches turn. Contact Lawrence Tognetti |
