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Get Velocity from Motors VI

LabVIEW 2013 Robotics Module Help

Edition Date: June 2013

Part Number: 372983D-01

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Owning Palette: Steering VIs

Requires: Robotics Module

Calculates the steering frame velocity or arc velocity required to best satisfy the velocity and angle of each motor. You must manually select the polymorphic instance to use.

Examples

Use the pull-down menu to select an instance of this VI.

Get Steering Frame Velocity from Motors

wheel indexes specifies the indexes of the wheels on which to operate, where 0 corresponds to the first wheel you added to the steering frame, 1 corresponds to the second wheel, and so on.
steering frame in is a reference to the steering frame on which to operate. Use the Create Steering Frame VI to generate this LabVIEW class object.
ccw motor velocity states is an array in which each element contains the velocity at which a motor moves to achieve the estimated steering frame velocity or estimated arc velocity. Use the Motor Communication VIs to generate the input velocity setpoints.
ccw motor angle states is an array in which each elements contains the angle of a motor that achieves the estimated steering frame velocity or estimated arc velocity. Use the Motor Communication VIs to generate the input angle setpoints.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
ccw caster motor velocity states is an array in which each element contains the rate of rotation of a caster wheel motor. If a motor is not associated with a caster wheel, LabVIEW returns 0.
steering frame out is a reference to the steering frame. You can wire this output to other Steering VIs.
estimated steering frame velocity contains a calculation of velocity of the steering frame in the form of [x_dot, y_dot, theta_dot] where x_dot is the velocity in the lateral, or right, direction, y_dot is the velocity in the forward direction, and theta_dot is angular velocity in the counterclockwise direction.
error out contains error information. This output provides standard error out functionality.

Get Arc Velocity from Motors

wheel indexes specifies the indexes of the wheels on which to operate, where 0 corresponds to the first wheel you added to the steering frame, 1 corresponds to the second wheel, and so on.
steering frame in is a reference to the steering frame on which to operate. Use the Create Steering Frame VI to generate this LabVIEW class object.
ccw motor velocity states is an array in which each element contains the velocity at which a motor moves to achieve the estimated steering frame velocity or estimated arc velocity. Use the Motor Communication VIs to generate the input velocity setpoints.
ccw motor angle states is an array in which each elements contains the angle of a motor that achieves the estimated steering frame velocity or estimated arc velocity. Use the Motor Communication VIs to generate the input angle setpoints.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
ccw caster motor velocity states is an array in which each element contains the rate of rotation of a caster wheel motor. If a motor is not associated with a caster wheel, LabVIEW returns 0.
steering frame out is a reference to the steering frame. You can wire this output to other Steering VIs.
estimated arc velocity is a cluster that contains the following elements.
turning radius contains the calculated turning radius of the circular arc. A value greater than 0 indicates counterclockwise rotation, and a value less than 0 indicates clockwise rotation.
tangential velocity contains the velocity of the vehicle in the direction tangential to the circular arc, or perpendicular to a line between the center of the circle and the vehicle.
angle from tangent (rad) contains the angle of the steering frame, measured counterclockwise from the vector tangent to the circular arc.
error out contains error information. This output provides standard error out functionality.

Examples

Refer to the following VIs for examples of using the Get Velocity from Motors VI:

  • labview\examples\robotics\Steering\3D Mecanum Robot\3D Mecanum Robot.lvproj
  • labview\examples\robotics\Steering\3D Omni Robot\3D Omni Robot.lvproj

 

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