SimMechanics™

Driver Actuator

Apply relative motion between a pair of constrained bodies through driver

Library

Sensors & Actuators

Description

The Driver Actuator block actuates a Driver block connected between a pair of bodies. You connect the block to the Driver block connected between the Bodies. The Driver block represents a time-dependent (rheonomic) constraint on a relative degrees of freedom (DoF) between the two bodies. A Driver requires a time-dependent function to specify the relative position, velocity, and acceleration of the connected Bodies. The output of the Driver Actuator is this time-dependent function f(t) and its first two derivatives.

You specify these three functions as a bundled Simulink^® input signal. This signal can be any Simulink signal, including a signal feedback from a Sensor block, satisfying these conditions:

The signal must consist of three bundled components.
- Exception: The Velocity Driver requires two bundled components.
The three components must be ordered [f(t), df(t)/dt, d²f(t)/dt²].
- Exception: The Velocity Driver requires a function and its derivative [f(t), df(t)/dt].
Each successive signal component must be the time derivative of the previous component.
The specific meaning of f(t) depends on the connected Driver block being actuated. Select the specific Driver block for details.
Linear Motions Angular Motions

Distance Driver
Linear Driver
Velocity Driver Angle Driver

Linear Motions	Angular Motions
Distance Driver Linear Driver Velocity Driver	Angle Driver

The Driver connects a base (B) and a follower (F) Body. The base-follower sequence determines the sense of the actuation signal. The inport is the Simulink input signal. The output is the follower you connect to the Driver block you want to actuate.

Tip You do not have to connect a Driver Actuator to a Driver block. If you do not actuate a Driver, the Driver block acts as a time-independent constraint that freezes the driven relative DoF between the Bodies at its initial value during the simulation.

Dialog Box and Parameters

The dialog has one active area, Actuation. The block parameters are not displayed unless you connect it to a specific Driver block.

Actuation

The block dialog parameters depend on the specific Driver block to which you have connected it.

Driving Linear Motion

Position units: In the pull-down menu, choose the units of the actuating f(t) you apply to the relative motion of the bodies. The default is m (meters).
Velocity units: In the pull-down menu, choose the units of the actuating df(t)/dt you apply to the relative motion of the bodies. The default is m/s (meters/second).
Acceleration units: In the pull-down menu, choose the units of the actuating d²f(t)/dt² you apply to the relative motion of the bodies. The default is m/s² (meters/second²).

Driving Angular Motion

Angular units: In the pull-down menu, choose the units of the actuating f(t) you apply to the relative motion of the bodies. The default is deg (degrees).
Angular velocity units: In the pull-down menu, choose the units of the actuating df(t)/dt you apply to the relative motion of the bodies. The default is deg/s (degrees/second).
Angular acceleration units: In the pull-down menu, choose the units of the actuating d²f(t)/dt² you apply to the relative motion of the bodies. The default is deg/s² (degrees/second²).

Example

Here is a Driver Actuator connected to a Distance Driver, which connects two Bodies:

You must add an Actuator port (connector port) to the Driver block to connect the Driver Actuator to it. The base (B)-follower (F) Body sequence on the two sides of the Driver determines the sense of the Driver Actuator data.

The Driver Actuator drives the relative motion between the two Bodies connected to the Driver. The nature of the connected Driver block determines the exact meaning of the actuation data, including the choice of units.