SimMechanics    
Distance Driver

Specify the distance between two Body CS origins as a function of time

Library

Constraints & Drivers

Description

The Distance Driver block drives the distance between the origins of two Body coordinate system (CS) as a function of time that you specify. This function must always remain nonnegative during the simulation.

Let r1, r2 be the vector positions of the origins of CS1 on one Body, CS2 on the other Body. The Distance Driver specifies the scalar distance |r1 - r2| between these points as a function of time:

You connect the Distance Driver to a Driver Actuator block.

The Simulink input signal into the Driver Actuator specifies the time-dependent driving function f(t) and its first two derivatives, as well as their units. If you do not actuate Distance Driver, this block acts as a time-independent constraint that freezes the distance between the two Body CSs at its initial value during the simulation.

Drivers restrict relative degrees of freedom (DoFs) between a pair of bodies as specified functions of time. Locally in a machine, they replace a Joint as the expression of the DoFs. Globally, Driver blocks must occur topologically in closed loops. Like Bodies connected to a Joint, the two Bodies connected to a Drivers are ordered as base and follower, fixing the direction of relative motion.

You can also connect a Driver block to a Constraint & Driver Sensor, which measures the reaction forces/torques between the driven bodies.

Dialog Box and Parameters

The dialog box has one active area, Connection parameters.

Connection Parameters

Current base
When you connect the base (B) Connector Port on the Distance Driver block to a Body CS Port on a Body, this parameter is automatically reset to the name of this Body CS. See the following Distance Driver base and follower Body Connector Ports figure.
Current follower
When you connect the follower (F) Connector Port on the Distance Driver block to a Body CS Port on a Body, this parameter is automatically reset to the name of this Body CS. See the following Distance Driver base and follower Body Connector Ports figure.
Number of sensor/actuator ports
Using this spinner menu, you can set the number of extra Connector Ports needed for connecting Driver Actuator and Constraint & Driver Sensor blocks to this Driver. The default is 0.
To activate the Driver, connect a Driver Actuator.

The base (B)-follower (F) Body sequence determines the sense of positive motion. Positive translation is the follower moving in the direction of the translation axis.

Distance Driver base and follower Body Connector Ports

See Also

Constraint & Driver Sensor, Driver Actuator, Linear Driver, Weld

See Modeling Constraints and Drivers for more on restricting DoFs with Drivers.

See Checking Schematic Topology and How SimMechanics Works for more on using drivers in closed loops.

See Creating Constraints and Drivers.


  Disassembled Spherical Driver Actuator