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dynamixel wheel mode

asked 2015-06-16 08:50:10 -0500

rmoncrief gravatar image

updated 2015-06-16 15:32:53 -0500

130s gravatar image

I am trying to put my dynamixel mx-64 servo motor into wheel mode like it says in step 1 of this tutorial http://wiki.ros.org/dynamixel_control... can anyone explain to me how to put the motor into wheel mode on ubuntu?

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Did u managed to apply torque control?

zweistein gravatar image zweistein  ( 2016-02-11 03:00:41 -0500 )edit

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answered 2016-01-19 04:00:14 -0500

roxane gravatar image

Hi,

I had the same problem, and I realised that putting the dynamixel in wheel mode is the same as setting CW angle and CCW angle to 0:

 rosrun dynamixel_driver set_servo_config.py 1 --cw-angle-limit=0 --ccw-angle-limit=0

"1" states for your motor ID. If you get the following message, then your motor is set to wheel mode:

Configuring Dynamixel motor with ID 1
Setting CW angle limit to 0
Setting CCW angle limit to 0
done

However, I found that there are some issues in this mode for AX-12A: for the range of angle values that are not available in standard mode, the velocity and load values are all wrong. Here are some values I get:

current load:  0.03515625
current vel =  0.79042471074
current load:  0.03515625
current vel =  0.79042471074
current load:  0.10546875
current vel =  0.37196456976
current load:  0.10546875
current vel =  0.37196456976
current load:  0.10546875
current vel =  0.37196456976
current load:  0.16796875
current vel =  0.0
current load:  0.16796875
current vel =  0.0
current load:  0.82421875
current vel =  -27.7229843399
current load:  0.82421875
current vel =  -27.7229843399
current load:  0.82421875
current vel =  -27.7229843399
current load:  0.50390625
current vel =  -7.96236657142
current load:  0.50390625
current vel =  -7.96236657142
current load:  0.50390625
current vel =  -7.96236657142
current load:  0.16796875
current vel =  0.0
current load:  0.16796875
current vel =  0.0
current load:  0.14453125
current vel =  0.13948671366
current load:  0.14453125
current vel =  0.13948671366
current load:  0.14453125
current vel =  0.13948671366
current load:  0.05078125
current vel =  0.6974335683
current load:  0.05078125
current vel =  0.6974335683

The range [0.03 0.05] for the load and [0.69 0.79] for the velocity are correct, but then they take unexpected values, such as 0.82 for the load and -27 for the velocity. Did anyone encountered such issue? I think the problem might be in the joint_position_controller.py file in the dynamixel_controller package, when state is defined with the function filter:

def process_motor_states(self, state_list):
        if self.running:
            state = filter(lambda state: state.id == self.motor_id, state_list.motor_states)
            if state:
                state = state[0]
                self.joint_state.motor_temps = [state.temperature]
                self.joint_state.goal_pos = self.raw_to_rad(state.goal, self.initial_position_raw, self.flipped, self.RADIANS_PER_ENCODER_TICK)
                self.joint_state.current_pos = self.raw_to_rad(state.position, self.initial_position_raw, self.flipped, self.RADIANS_PER_ENCODER_TICK)
                self.joint_state.error = state.error * self.RADIANS_PER_ENCODER_TICK
                self.joint_state.velocity = state.speed * self.VELOCITY_PER_TICK
                self.joint_state.load = state.load
                self.joint_state.is_moving = state.moving
                self.joint_state.header.stamp = rospy.Time.from_sec(state.timestamp)

                self.joint_state_pub.publish(self.joint_state)

I just cannot find any description of this filter function to look into it.

If anyone has an answer for this, it would be very helpful.

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Comments

I have the motors mounted in a robot arm, how can I check the initial values of CW angle and CCW angle, so I can set them to (0,0) and then back to the original setup?

zweistein gravatar image zweistein  ( 2016-02-11 03:04:00 -0500 )edit
0

answered 2015-06-16 15:02:32 -0500

130s gravatar image

updated 2015-06-16 15:33:29 -0500

I hope I'm wrong but the operating mode might be hardcoded per the product model and there might not be a way to change them programatically. For example:

DXL_MODEL_TO_PARAMS = \
{
    113: { 'name':               'DX-113',
           'encoder_resolution': 1024,
           'range_degrees':      300.0,
           'torque_per_volt':    1.0 / 12.0,                       #  1.0 NM @ 12V
           'velocity_per_volt':  (54 * RPM_TO_RADSEC) / 12.0,      #  54 RPM @ 12V
           'rpm_per_tick':       0.111,
           'features':           []
         },
:
     12: { 'name':               'AX-12',
           'encoder_resolution': 1024,
           'range_degrees':      300.0,
           'torque_per_volt':    1.5 / 12.0,                       #  1.5 NM @ 12V
           'velocity_per_volt':  (59 * RPM_TO_RADSEC) / 12.0,      #  59 RPM @ 12V
           'rpm_per_tick':       0.111,
           'features':           []
         },
:
    320: { 'name':               'MX-106',
           'encoder_resolution': 4096,
           'range_degrees':      360.0,
           'torque_per_volt':    8.4 / 12.0,                       #  8.4 NM @ 12V
           'velocity_per_volt':  (45 * RPM_TO_RADSEC) / 12.0,      #  45 RPM @ 12.0V
           'rpm_per_tick':       0.114,
           'features':           [DXL_CURRENT_L, DXL_TORQUE_CONTROL_MODE, DXL_GOAL_ACCELERATION]
         },
}

You could submit a feature request on the issue tracker but since the development is stale, sending a pull request might be the best idea.

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Asked: 2015-06-16 08:46:36 -0500

Seen: 1,577 times

Last updated: Jun 16 '15