Changes between Initial Version and Version 1 of Hand/282/ControlModes

Timestamp:

Jan 11, 2016, 7:39:14 PM (9 years ago)

Author:

cv

Comment:

--

Hand/282/ControlModes

@@ +1 @@
+The BarrettHand has several control modes:
+
+* Torque (MODE = 2, TSTOP = 0) - You can stream torque commands to each
+of the four motors (or any subset) while receiving joint position
+feedback. The actual torques applied at the finger joints are only
+loosely related to the commanded motor torques because of the large
+amount of friction introduced by the worm drives. If you want to use
+torque control, you should implement your own higher-level control
+wrapper around the torque (using position or velocity). You must also
+keep track of the finger speeds, motor temperature, and joint limits
+yourself to prevent damage to the BarrettHand. We recommend an update
+rate of at least 200Hz to maintain smooth motions in this mode.
+
+* Position (MODE = 3, TSTOP = 0) - You can stream position commands to
+each of the four motors (or any subset). The BarrettHand will attempt to
+reach the desired position instantly using its PID gain properties KP,
+KD, and KI. You must not give the BarrettHand a set of positions that is
+too far from the present position or else the controller will go
+unstable. You should write your own position profile generator and use
+the encoder positions as feedback. We recommend an update rate of at
+least 50Hz in order to maintain smooth motions in this mode. The
+BarrettHand is aware of its own joint stops in this mode and will not
+let you drive the fingers past their joint stops. However, you must
+limit the finger velocities with your own controller.
+
+* Velocity (MODE = 4, TSTOP = 0) - You can stream velocity commands to
+each of the four motors (or any subset). The BarrettHand will maintain
+the previously sent velocity until a new velocity command is received.
+The BarrettHand is aware of its own joint stops in this mode and will
+not let you drive the fingers past their joint stops. The BarrettHand
+will also limit the max finger velocity in this mode (to property MV).
+There is no minimum recommended update rate, so this mode works well for
+high-latency applications.
+
+* Trapezoidal velocity profile (MODE = 5, TSTOP = 1) - You can send
+discrete target endpoint positions (property E) to each of the four
+motors (or any subset). The BarrettHand will generate its own
+trapezoidal velocity profile to accelerate from its present position
+(using ACCEL) until it reaches max velocity (MV), then it will
+decelerate to reach the target endpoint position at zero velocity. You
+should not stream positions in this mode. This mode is intended for
+discrete motion commands separated in time, usually several seconds
+apart. The BarrettHand is aware of its own joint stops in this mode and
+will not let you drive the fingers past their joint stops. The
+BarrettHand will also limit the max finger velocity in this mode (to
+property MV). There is no minimum recommended update rate, so this mode
+works well for high-latency applications. However you should not send a
+new endpoint value until the present motion is complete. The MODE
+property of each finger will drop from 5 (TRAP) to either 3 (POS) or 0
+(IDLE) when the motion is complete. If the HOLD property is set to 1,
+the MODE will drop from 5 to 3, and the finger will actively hold
+position at the end of a trapezoidal move. If the HOLD property is set
+to 0, the MODE will drop from 5 to 0, and the motor will be able to move
+freely at the end of a trapezoidal move. The HOLD property is especially
+applicable to the "Spread" motor as it is driven by a backdrivable spur
+gear instead of a non-backdrivable worm gear as is found in the finger
+motor drives.