Ideal Rotational Motion Sensor

Motion sensor in mechanical rotational systems

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• Simscape / Foundation Library / Mechanical / Mechanical Sensors

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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 = ω_R – ω_C, where ω_R, ω_C 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

W — Angular velocity, rad/s

physical signal

Physical signal output port for angular velocity.

A — Angular displacement, rad

physical signal

Physical signal output port for angular displacement.

Conserving

R — Rod (positive probe)

mechanical rotational

Mechanical rotational conserving port associated with the sensor positive probe.

C — Case (reference probe)

mechanical rotational

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

Parameters

Wrap angle to [0, 2*pi] — Control output range for angular displacement

Off (default) | On

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.

Initial angle — Sensor initial offset

0 rad (default)

Sensor initial angular position (offset).

Model Examples

Permanent Magnet DC Motor

This model is based on a Faulhaber Series 0615 DC-Micromotor. The parameters values are set to match the 1.5V variant of this motor. The model uses these parameters to verify manufacturer-quoted no-load speed, no-load current, and stall torque.

Mechanical Rotational System with Stick-Slip Motion

A mechanical rotational system with stick-slip friction. An inertia is connected to a fixed point by spring and damper. The inertia is driven by a velocity source via a stick-slip friction element. The friction element has a difference between the breakaway and the Coulomb frictions, resulting in stick-slip motion of the inertia.

Extended Capabilities

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