Ideal Translational Motion Sensor

Motion sensor in mechanical translational systems

• 

Libraries:
Simscape / Foundation Library / Mechanical / Mechanical Sensors

Description

The Ideal Translational Motion Sensor block represents a device that converts an across variable measured between two mechanical translational nodes into a control signal proportional to acceleration, velocity, or position. You can specify the initial position (offset) as a block parameter.

The sensor is ideal since it does not account for inertia, friction, delays, energy consumption, and so on.

Connections R and C are mechanical translational conserving ports that connect the block to the nodes where motion is being monitored. The block positive direction is from port R to port C. This means that the velocity is measured as v = v_R – v_C, where v_R, v_C are the absolute velocities at ports R and C, respectively. The Measurement reference parameter lets you disable port C and measure with respect to ground.

Connections A, V, and P are physical signal output ports for acceleration, velocity, and position, respectively. The visibility of these ports is controlled by block parameters. If you enable port A, the block performs additional computations, to measure acceleration based on velocity. To avoid unnecessary model complexity, it is recommended that in each instance of the block you enable only the ports that you actually use for measurement.

Examples

Mass-Spring-Damper with Controller

A controlled mass-spring-damper. A controller adjusts the force on the mass to have its position track a command signal. The initial velocity for the mass is 10 meters per second. The controller adjusts the force applied by the Force Source to track the step changes to the input signal.

• Open Model

Linkage Mechanism

The use of the Simscape™ Lever block in a linkage mechanism. Lever 1 and Lever 4 are first class levers with the fulcrum at the end. Lever 3 is a second class lever with the fulcrum in the middle. Lever 2 is a summing lever driven by the first and the third levers.

• Open Model

Mechanical System with Translational Hard Stop

Two masses connected by a hard stop. Mass 1 is driven by an Ideal Velocity Source. As the velocity input changes direction, Mass 2 will stay at rest until Mass 1 reaches the other end of the backlash modeled by the Translational Hard Stop. Plotting the displacement of Mass 2 against the displacement of the Mass 1 produces a typical hysteresis curve.

• Open Model

Ports

Output

A — Acceleration, m/s^2

physical signal

Physical signal output port for acceleration.

Dependencies

To enable this port, select the Acceleration check box.

V — Velocity, m/s

physical signal

Physical signal output port for velocity.

Dependencies

To enable this port, select the Velocity check box.

P — Position, m

physical signal

Physical signal output port for position.

Dependencies

To enable this port, select the Position check box.

Conserving

R — Rod (positive probe)

mechanical translational

Mechanical translational conserving port associated with the sensor positive probe.

C — Case (reference probe)

mechanical translational

Mechanical translational conserving port associated with the sensor negative (reference) probe.

Dependencies

To enable this port, set the Measurement reference parameter to Difference.

Parameters

Measurement reference — Select whether to perform absolute or relative measurements

Difference (default) | Absolute

Select whether to perform absolute or relative measurements:

• Difference — Measure the acceleration, velocity, and position of port R relative to port C.

• Absolute — Disable port C and measure the acceleration, velocity, and position of port R with respect to ground (internal reference node).

Acceleration — Control output port visibility to measure acceleration

off (default) | on

Selecting this check box exposes output port A, which lets you measure acceleration. Exposing port A also involves additional computations, to measure acceleration based on velocity, therefore this port is off by default.

Velocity — Control output port visibility to measure velocity

on (default) | off

Selecting this check box exposes output port V, which lets you measure velocity.

Position — Control output port visibility to measure position

on (default) | off

Selecting this check box exposes output port P, which lets you measure position.

Initial position — Sensor initial offset

0 m (default)

Sensor initial position (offset).

Dependencies

To enable this parameter, select the Position check box.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2007a

R2022b: Measure acceleration, measure with respect to ground, and parametrically control visibility of output ports

The block enhancements include:

• An additional physical signal output port, A, that lets you measure acceleration.

• Additional parameters (Acceleration, Velocity, and Position) that control the visibility of physical signal output ports, letting you expose only the ports that are actually used for measurement in each particular instance. This enhancement helps improve the block diagram readability. Also, because exposing the acceleration measurement port involves additional computations, this port is hidden by default and it is recommended that you do not expose it unless you need to measure acceleration.

• In previous releases, the blocks measured only relative velocity and position of port R with respect to port C. Now, the new Measurement reference parameter lets you disable port C and measure with respect to ground (internal reference node).

These enhancements have no compatibility impact on models created in previous releases.