Speed Measurement

Compute speed from rotor angular position

• Library:

• Motor Control Blockset / Sensor Decoders

• 

Description

The Speed Measurement block calculates the angular speed from the angular position of the rotor by calculating the change in the angular position with respect to time.

Ports

Input

θ — Angular position of rotor

scalar

Angular position of the rotor specified in either radians, degrees, or per-unit.

Data Types: single | double | fixed point

Output

⍵ — Angular speed of rotor

scalar

Angular speed that the block computes based on the angular position input.

Data Types: single | double | fixed point

Parameters

Position unit — Unit of angular position

Radians (default) | Degrees | Per unit

Unit of the angular position θ.

Speed calculation criteria — Method of speed calculation

Maximum application speed (default) | Speed resolution | Time interval for speed calculation

The speed calculation method used in the block. The selected method determines the range of the rotor speed that the block can measure.

These parameters change values according to the Speed calculation criteria parameter:

Parameter name	Maximum application speed	Speed Resolution	Time interval for speed calculation
Delays for speed calculation (number of samples)	299	28	28
Maximum measurable speed (RPM)	1000	10344.8276	10713.2857
Measurable speed resolution (RPM)	4.6566e-07	4.9892e-06	4.9892e-06

Block sample time (S) — Sample time after which block executes again

100e-6 (default) | scalar

The fixed time interval (in seconds) between every two consecutive instances of block execution.

These parameters change values according to the Block sample time (S) parameter value:

• Delays for speed calculation (number of samples)

• Maximum measurable speed (RPM)

• Measurable speed resolution (RPM)

Maximum application speed (RPM) — Maximum measurable rotor speed

1000 (default) | scalar

The maximum rotor speed (in rotations per minute) that the block can measure.

These parameters change values according to the Maximum application speed (RPM) parameter value:

• Delays for speed calculation (number of samples)

• Maximum measurable speed (RPM)

• Measurable speed resolution (RPM)

Dependencies

To enable this parameter, set Speed calculation criteria to Maximum application speed.

Speed Resolution (RPM) — Minimum detectable value of change in angular position

5e-6 (default) | scalar

The minimum value of the θ input that the block can detect.

These parameters change values according to the Speed Resolution (RPM) parameter value:

• Delays for speed calculation (number of samples)

• Maximum measurable speed (RPM)

• Measurable speed resolution (RPM)

Delays for speed calculation (number of samples) — Number of angular position samples measured

299 or 28 (default) | scalar

The number of samples of the angular position input that the block measures to compute the average position value.

These parameters change values according to the Delays for speed calculation (number of samples) parameter value:

• Maximum measurable speed (RPM)

• Measurable speed resolution (RPM)

Dependencies

To enable this parameter, set Speed calculation criteria to Time interval for speed calculation.

Speed unit — Unit of angular speed output

RPM (default) | Degrees/Sec | Radians/Sec | Per unit based on maximum measurable speed | Per unit based on dialog

Unit of the angular speed output.

Speed data type — Data type of angular speed output

single (default) | double | fixed point

The data type of the angular speed output ⍵.

Note

The Speed Measurement block may occasionally display the warning message 'Wrap on overflow detected.'

Extended Capabilities

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

Fixed-Point Conversion
Design and simulate fixed-point systems using Fixed-Point Designer™.

Introduced in R2020a