Speed Measurement

Compute speed from rotor angular position

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Libraries:
Motor Control Blockset / Sensor Decoders
Motor Control Blockset HDL Support / 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.

Examples

Field-Oriented Control of Induction Motor Using Speed Sensor

Implements the field-oriented control (FOC) technique to control the speed of a three-phase AC induction motor (ACIM). The FOC algorithm requires rotor speed feedback, which is obtained in this example by using a quadrature encoder sensor. For details about FOC, see Field-Oriented Control (FOC).

• Open Model

Field-Weakening Control (with MTPA) of PMSM

Implements the field-oriented control (FOC) technique to control the torque and speed of a three-phase permanent magnet synchronous motor (PMSM). The FOC algorithm requires rotor position feedback, which is obtained by a quadrature encoder sensor. For details about FOC, see Field-Oriented Control (FOC).

• Open Model

Field-Oriented Control of PMSM Using Hall Sensor

Implements the field-oriented control (FOC) technique to control the speed of a three-phase permanent magnet synchronous motor (PMSM). The FOC algorithm requires rotor position feedback, which is obtained by a Hall sensor. For details about FOC, see Field-Oriented Control (FOC).

• Open Model

Field-Oriented Control of PMSM Using Quadrature Encoder

Implements the field-oriented control (FOC) technique to control the speed of a three-phase permanent magnet synchronous motor (PMSM). The FOC algorithm requires rotor position feedback, which is obtained by a quadrature encoder sensor. For details about FOC, see Field-Oriented Control (FOC).

• Open Model

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

Ts — Sample time after which block executes again

scalar

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

Dependencies

To enable this port, select the Advanced Options > Use input port for Discrete step size parameter.

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

The unit of the angular position θ.

Position scaling datatype — Range for mapping input position

uint32 (default) | uint16 | uint64

Range used to map input position internally to fit in the unsigned integer datatype. For example, the block scales an input in the range (0 - 2π) to (0 - (232-1)) for uint32 datatype.

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

Discrete step size (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 Discrete step size (s) parameter value:

• Delays for speed calculation (number of samples)

• Maximum measurable speed (RPM)

• Measurable speed resolution (RPM)

Dependencies

To enable this parameter, clear the Advanced Options > Use input port for Discrete step size parameter.

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 speed

5e-6 (default) | scalar

The minimum value of change in the θ input per unit time 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)

Dependencies

To enable this parameter, set Speed calculation criteria to Speed resolution.

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)

Note

The maximum limit for Delays for speed calculation (number of samples) parameter is set at 2^30 (or 1073741824). This limit affects the values of Maximum measurable speed (RPM) and Measurable speed resolution (RPM) parameters, and they may not always match the desired values.

Dependencies

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

Maximum measurable speed (RPM) — Maximum measurable speed

1000 or 10344.8276 or 10713.2857 (default) | scalar

The absolute maximum speed that the block can measure.

This parameter is not configurable and uses a value that is internally computed using other parameters.

Measurable speed resolution (RPM) — Minimum speed resolution used for speed computation

4.6566e-07 or 4.9892e-06 (default) | scalar

The minimum speed resolution that the block uses for speed computation. It is always less than or equal to Speed Resolution (RPM).

This parameter is not configurable and uses a value that is internally computed using other parameters.

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.

Per unit speed (RPM) — Speed (in RPM) for per-unit calculation

1000 (default)

Specify the speed in RPM for per-unit calculation.

Dependencies

This parameter appears only if Per unit based on dialog is selected for Speed unit.

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.'

Use input port for Discrete step size — Specify sample step size with input port

off (default) | on

Select this parameter if you want to specify the sample step size using an input port.

Extended Capabilities

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

HDL Code Generation

Generate VHDL, Verilog and SystemVerilog code for FPGA and ASIC designs using HDL Coder™.

HDL Coder™ provides additional configuration options that affect HDL implementation and synthesized logic.

HDL Architecture

This block has a single, default HDL architecture.

HDL Block Properties

ConstrainedOutputPipeline	Number of registers to place at the outputs by moving existing delays within your design. Distributed pipelining does not redistribute these registers. The default is 0. For more details, see ConstrainedOutputPipeline (HDL Coder).
InputPipeline	Number of input pipeline stages to insert in the generated code. Distributed pipelining and constrained output pipelining can move these registers. The default is 0. For more details, see InputPipeline (HDL Coder).
OutputPipeline	Number of output pipeline stages to insert in the generated code. Distributed pipelining and constrained output pipelining can move these registers. The default is 0. For more details, see OutputPipeline (HDL Coder).
SharingFactor	Number of functionally equivalent resources to map to a single shared resource. The default is 0. See also Resource Sharing (HDL Coder).

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

Version History

Introduced in R2020a

R2025a: New input port and block parameters added

The Block Parameters dialog box now includes the Use input port for Discrete step size parameter for you to specify a discrete step size from a separate input port Ts.