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Apply Velocity to 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 velocity and angle of each motor necessary to satisfy the steering frame velocity or arc velocity at the center of a steering frame. You must manually select the polymorphic instance to use.

Examples

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

Apply Steering Frame Velocity to 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.
steering frame velocity specifies the 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 the angular velocity in the counterclockwise direction.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
constraint error tolerance is the maximum allowable difference between the value this VI calculates for the steering angle of a wheel and possible values for the steering angle given kinematic constraints of the steering frame. If the difference is greater than constraint error tolerance, LabVIEW returns a warning with the name of the last wheel whose steering angle is out of range. The default is 1E-12.
steering frame out is a reference to the steering frame. You can wire this output to other Steering VIs.
ccw motor velocity setpoints returns an array in which each element returns the velocity at which a motor must move to achieve the input velocity.
ccw motor angle setpoints returns an array in which each element returns the angle of a motor that achieves the input velocity.
error out contains error information. This output provides standard error out functionality.
ccw caster motor velocity setpoints is an array in which each element returns the rate of rotation of a caster wheel motor that achieves the input velocity. If a motor is not associated with a caster wheel, LabVIEW returns 0.

Apply Arc Velocity to 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.
arc velocity is a cluster whose elements define the arc velocity of the steering frame.
turning radius specifies the 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 specifies 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) specifies the angle of the steering frame, measured counterclockwise from the vector tangent to the circular arc.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
constraint error tolerance is the maximum allowable difference between the value this VI calculates for the steering angle of a wheel and possible values for the steering angle given kinematic constraints of the steering frame. If the difference is greater than constraint error tolerance, LabVIEW returns a warning with the name of the last wheel whose steering angle is out of range. The default is 1E-12.
steering frame out is a reference to the steering frame. You can wire this output to other Steering VIs.
ccw motor velocity setpoints returns an array in which each element returns the velocity at which a motor must move to achieve the input velocity.
ccw motor angle setpoints returns an array in which each element returns the angle of a motor that achieves the input velocity.
error out contains error information. This output provides standard error out functionality.
ccw caster motor velocity setpoints is an array in which each element returns the rate of rotation of a caster wheel motor that achieves the input velocity. If a motor is not associated with a caster wheel, LabVIEW returns 0.

Examples

Refer to the following VIs for examples of using the Apply Velocity to 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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