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Get Velocity from Wheels 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 state of each wheel. You can read data for each wheel from wheel motors or specify the wheel data manually. You must manually select the polymorphic instance to use.

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

Get Steering Frame Velocity from Wheels

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.
get motor data determines whether this VI reads wheel information from motors configured for individual wheels. The default is FALSE, which means you must specify acquired wheel states.
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.
acquired wheel states is an array of clusters that define the condition of each wheel on the steering frame. If get motor data is TRUE, LabVIEW ignores acquired wheel states and reads wheel information from motors. If get motor data is FALSE and you do not specify values for acquired wheel states, LabVIEW returns default values in wheel states.
wheel name specifies the identifier for the wheel.
forward angular velocity specifies the rate of rotation, in radians per second, of the wheel in the forward direction.
caster angular velocity specifies the rate of rotation of a caster wheel around the wheel pivot that attaches to the steering frame.
caster wheel angle (rad) specifies the orientation of a caster wheel with respect to the wheel pivot that attaches to the steering frame.
steering angle (rad) specifies the orientation of the wheel with respect to the wheel frame. For example, a steering angle of 0 means the wheel is oriented straight given the wheel frame angle.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
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.
wheel states is an array of clusters that define the state of each wheel on the steering frame. If get motor data is TRUE, LabVIEW returns wheel data from wheel motors. Otherwise, LabVIEW returns the values in acquired wheel states.
wheel name contains the identifier for the wheel.
forward angular velocity contains the rate of rotation, specified in radians per second, of the wheel in the forward direction.
caster angular velocity contains the rate of rotation of a caster wheel around the wheel pivot that attaches to the steering frame. If the wheel is not a caster wheel, LabVIEW returns 0.
caster wheel angle (rad) contains the orientation of a caster wheel with respect to the wheel pivot that attaches to the steering frame. If the wheel is not a caster wheel, LabVIEW returns 0.
steering angle (rad) contains the orientation of the wheel with respect to the wheel frame. If the wheel is not a steering wheel, LabVIEW returns 0.
error out contains error information. This output provides standard error out functionality.

Get Arc Velocity from Wheels

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.
get motor data determines whether this VI reads wheel information from motors configured for individual wheels. The default is FALSE, which means you must specify acquired wheel states.
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.
acquired wheel states is an array of clusters that define the condition of each wheel on the steering frame. If get motor data is TRUE, LabVIEW ignores acquired wheel states and reads wheel information from motors. If get motor data is FALSE and you do not specify values for acquired wheel states, LabVIEW returns default values in wheel states.
wheel name specifies the identifier for the wheel.
forward angular velocity specifies the rate of rotation, in radians per second, of the wheel in the forward direction.
caster angular velocity specifies the rate of rotation of a caster wheel around the wheel pivot that attaches to the steering frame.
caster wheel angle (rad) specifies the orientation of a caster wheel with respect to the wheel pivot that attaches to the steering frame.
steering angle (rad) specifies the orientation of the wheel with respect to the wheel frame. For example, a steering angle of 0 means the wheel is oriented straight given the wheel frame angle.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
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.
wheel states is an array of clusters that define the state of each wheel on the steering frame. If get motor data is TRUE, LabVIEW returns wheel data from wheel motors. Otherwise, LabVIEW returns the values in acquired wheel states.
wheel name contains the identifier for the wheel.
forward angular velocity contains the rate of rotation, specified in radians per second, of the wheel in the forward direction.
caster angular velocity contains the rate of rotation of a caster wheel around the wheel pivot that attaches to the steering frame. If the wheel is not a caster wheel, LabVIEW returns 0.
caster wheel angle (rad) contains the orientation of a caster wheel with respect to the wheel pivot that attaches to the steering frame. If the wheel is not a caster wheel, LabVIEW returns 0.
steering angle (rad) contains the orientation of the wheel with respect to the wheel frame. If the wheel is not a steering wheel, LabVIEW returns 0.
error out contains error information. This output provides standard error out functionality.

 

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