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


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Timestamp:
Jan 11, 2016, 7:39:14 PM (9 years ago)
Author:
cv
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  • Hand/282/ControlModes

    v1 v1  
     1The BarrettHand has several control modes:
     2
     3* Torque (MODE = 2, TSTOP = 0) - You can stream torque commands to each
     4of the four motors (or any subset) while receiving joint position
     5feedback. The actual torques applied at the finger joints are only
     6loosely related to the commanded motor torques because of the large
     7amount of friction introduced by the worm drives. If you want to use
     8torque control, you should implement your own higher-level control
     9wrapper around the torque (using position or velocity). You must also
     10keep track of the finger speeds, motor temperature, and joint limits
     11yourself to prevent damage to the BarrettHand. We recommend an update
     12rate of at least 200Hz to maintain smooth motions in this mode.
     13
     14* Position (MODE = 3, TSTOP = 0) - You can stream position commands to
     15each of the four motors (or any subset). The BarrettHand will attempt to
     16reach the desired position instantly using its PID gain properties KP,
     17KD, and KI. You must not give the BarrettHand a set of positions that is
     18too far from the present position or else the controller will go
     19unstable. You should write your own position profile generator and use
     20the encoder positions as feedback. We recommend an update rate of at
     21least 50Hz in order to maintain smooth motions in this mode. The
     22BarrettHand is aware of its own joint stops in this mode and will not
     23let you drive the fingers past their joint stops. However, you must
     24limit the finger velocities with your own controller.
     25
     26* Velocity (MODE = 4, TSTOP = 0) - You can stream velocity commands to
     27each of the four motors (or any subset). The BarrettHand will maintain
     28the previously sent velocity until a new velocity command is received.
     29The BarrettHand is aware of its own joint stops in this mode and will
     30not let you drive the fingers past their joint stops. The BarrettHand
     31will also limit the max finger velocity in this mode (to property MV).
     32There is no minimum recommended update rate, so this mode works well for
     33high-latency applications.
     34
     35* Trapezoidal velocity profile (MODE = 5, TSTOP = 1) - You can send
     36discrete target endpoint positions (property E) to each of the four
     37motors (or any subset). The BarrettHand will generate its own
     38trapezoidal velocity profile to accelerate from its present position
     39(using ACCEL) until it reaches max velocity (MV), then it will
     40decelerate to reach the target endpoint position at zero velocity. You
     41should not stream positions in this mode. This mode is intended for
     42discrete motion commands separated in time, usually several seconds
     43apart. The BarrettHand is aware of its own joint stops in this mode and
     44will not let you drive the fingers past their joint stops. The
     45BarrettHand will also limit the max finger velocity in this mode (to
     46property MV). There is no minimum recommended update rate, so this mode
     47works well for high-latency applications. However you should not send a
     48new endpoint value until the present motion is complete. The MODE
     49property of each finger will drop from 5 (TRAP) to either 3 (POS) or 0
     50(IDLE) when the motion is complete. If the HOLD property is set to 1,
     51the MODE will drop from 5 to 3, and the finger will actively hold
     52position at the end of a trapezoidal move. If the HOLD property is set
     53to 0, the MODE will drop from 5 to 0, and the motor will be able to move
     54freely at the end of a trapezoidal move. The HOLD property is especially
     55applicable to the "Spread" motor as it is driven by a backdrivable spur
     56gear instead of a non-backdrivable worm gear as is found in the finger
     57motor drives.