# Ideal Rotational Motion Sensor

Motion sensor in mechanical rotational systems

• Library:
• Simscape / Foundation Library / Mechanical / Mechanical Sensors

## Description

The Ideal Rotational Motion Sensor block represents an ideal mechanical rotational motion sensor, that is, a device that converts an across variable measured between two mechanical rotational nodes into a control signal proportional to angular velocity or angle. You can specify the initial angular 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 rotational conserving ports that connect the block to the nodes whose motion is being monitored. Connections W and A are physical signal output ports for velocity and angular displacement, respectively.

The block positive direction is from port R to port C. This means that the velocity is measured as ω = ωRωC, where ωR, ωC are the absolute angular velocities at ports R and C, respectively.

The Wrap angle to [0, 2*pi] parameter lets you control the angular displacement output range. When set to `On`, it keeps angular displacement within the range from 0 to 2π radians (360 degrees), regardless of the number of revolutions performed by the object and the direction of rotation. When set to `Off`, the output range is unrestricted.

The figure demonstrates the difference between the two options.

In this example, the object is moving at 6 rad/s in the positive direction for the first 5 seconds, and then switches to the negative direction at the same speed. The default angular displacement output (line 1) shows that the object turned forward by 30 rad and then turned back in the negative direction, continuing until –20 rad. If you set Wrap angle to [0, 2*pi] to `On`, the output (line 2) stays in the range from 0 to 2π rad.

Setting the Wrap angle to [0, 2*pi] parameter to `On` simplifies development of models with complex relationship between model parameters and rotation angle, such as pumps and motors.

## Ports

### Output

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Physical signal output port for angular velocity.

Physical signal output port for angular displacement.

### Conserving

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Mechanical rotational conserving port associated with the sensor positive probe.

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

## Parameters

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When set to `On`, keeps angular displacement output by the sensor within the range from 0 to 2π radians (360 degrees), regardless of the number of revolutions performed by the object and the direction of rotation. When set to `Off`, the output range is unrestricted.

Setting this parameter to `On` simplifies development of models with complex relationship between model parameters and rotation angle, such as pumps and motors.

Sensor initial angular position (offset).