SimMechanics

Constraint & Driver Sensor

Measure constraint force/torque between a pair of constrained bodies

Library

Sensors & Actuators

Description

The Constraint & Driver Sensor block measures the force/torque of constraint (reaction force/torque) between a pair of bodies. You connect the block to the Constraint or Driver block connected between the two Bodies. The output signal is the reaction force/torque.

The Constraint & Driver Sensor measures the reaction force/torque in the reference coordinate system (CS) specified in the block dialog box. The Constraint or Driver block connects a base and a follower Body. You choose in the dialog box to measure the reaction force/torque on either the base or the follower Body.

The input is the connector port connected to the Constraint or Driver block you want to sense. The outport is a set of Simulink signals or one bundled Simulink signal of the reaction force/torque vector(s).

A body's orientation rotation matrix R relates vector components measured in the body CS and in the inertial World CS by [R]v_b = v_s. The column vector v_b lists the vector v's three components measured in the body CS. The column vector v_s lists the vector v's three components measured in the World CS.

Dialog Box and Parameters

The dialog box has one active area, Measurements.

Measurements

Reactions measured on

In the pull-down menu, choose to measure the reaction force/torque on the base (B) or follower (F) Body. The default is Base.

With respect to coordinate system

In the pull-down menu, choose the CS in which the reaction force/torque or motion is interpreted. The default is Absolute (World).

In the Absolute case, the force vectors have components measured relative to the inertial World CS axes. In the Local case, the same force vector signals are premultiplied by the inverse rotation matrix R^-1 = R^T for the Body selected in Reactions measured on.

Reaction torque

Select the check box if you want to measure the reaction torque. The default is selected. The torque is a row vector in the Simulink output signal.

In the pull-down menu, choose the units for the reaction torque. The default is N-m (Newton-meters).

Reaction force

Select the check box if you want to measure the reaction force. The default is selected. The force is a row vector in the Simulink output signal.

In the pull-down menu, choose the units for the reaction force. The default is N (Newtons).

Output selected parameters as one signal

Select this check box to convert the output signals into a single bundled signal. The default is selected. If you unselect it, the Constraint & Driver Sensor block will grow as many Simulink outports as there are active signals selected, in the same order top to bottom, in the dialog box.

If the check box is selected, the Simulink signal out has all the active signals bundled into a single row vector, ordered in the order shown in the dialog box. The type of the signal components depends on which measurements are active (selected).

Example

Here is a Constraint & Driver Sensor connected to a Gear Constraint, which connects and constraints two Bodies:

You must add a Sensor port (connector port) to the Constraint/Driver block to connect the Constraint & Driver Sensor to it. The base (B)-follower (F) Body sequence on the two sides of the Joint determines the sense of the Constraint & Driver Sensor data.

See Also

Body Sensor, Driver Actuator, Joint Sensor, Mechanical Branching Bar

See Representing Body Positions and Orientations and Modeling Sensors.

In Simulink, see the Signal Routing Library and the Sinks Library.

Connection Port

Continuous Angle