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Rotational Power Sensor

Measure average or instantaneous rotational power

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  • Rotational Power Sensor block

Libraries:
Simscape / Driveline / Sensors

Description

The Rotational Power Sensor block measures the rotational power change between ports R and C. The physical signal output can be an instantaneous or averaged value depending on what you select for the Measurement type parameter.

When you set:

  • Measurement type to Instantaneous power, the instantaneous power is the product of the current angular velocity and torque. Use this setting to analyze peak power transmission and identify heavily loaded components.

  • Measurement type to Average power over a specified period, the time-averaged power is the integral of the instantaneous power over one sample period, divided by that period. For simulation times smaller than the sample period, the average power is zero. The power output is constant for each sample period.

  • Measurement type to Average power over a vibration, the average vibration power is the integral of the power over one vibration period, divided by that period. The vibration period is the time between two consecutive crossings from negative to positive velocity values. If the vibration has a variable frequency, the averaging period can change. For simulation times smaller than the vibration period, the average power is zero. The power output is constant for each vibration period.

  • Measurement type to Average power over a revolution, the average revolution power is the integral of the instantaneous power over one revolution period, divided by that period. The revolution period is defined as the time between two consecutive crossings of zero angular position. If the revolution has a variable frequency, the averaging period can change. For simulation times smaller than the revolution period, the average power is zero. The power output is constant for each revolution period.

Examples

Gearbox Efficiency Measurement

Gearbox Efficiency Measurement

A test for measuring gear box efficiency. The input shaft is driven at a fixed speed and a variable torque is applied to the output shaft. Power is measured on both the input and output shafts, and efficiency is calculated as the ratio of output to input power. The simulation results match the parameters specified for the efficiency of the gear.

Epicyclic Gear Efficiency Measurement

Epicyclic Gear Efficiency Measurement

An epicyclic gear drive with overall ratio of 256:1 and verifies its transmission efficiency given the individual gear meshing efficiencies. The example is based on Tuplin, W.A. "Designing Compound Epicyclic Gear Trains for Maximum Speed at High Velocity Ratios", Machine Design, April 4, 1957. The drive is built of two ring-planet elements as shown in the gearbox schematic. The example confirms the transmission efficiency value of 0.22 as predicted by the analytical analysis presented in the paper.

Variable Ratio Gear

Variable Ratio Gear

A variable ratio gear coupling two inertias (shafts). The gear ratio between the follower (F) and the base (B) is steadily increased from 1:1 to 2:1. The ratio of the follower to base angular speed decreases with gear ratio, and conversely the ratio of the follower to base torque increases with gear ratio. The variable gear is implemented using the Variable Ratio Transmission block which includes compliance. Appropriate stiffness and damping values for the compliance will depend upon the levels of torque transmitted by the variable gear. If the compliance damping is unrealistically low, the system can develop high frequency oscillations that require small simulation time steps.

Transmission Testbed

Transmission Testbed

A testbed with interchangeable transmissions. The transmission models vary from classic four speed transmissions to modern seven, eight, nine, and ten speed configurations. The efficiency and drive ratio can be adjusted by varying the components in each individual transmission configuration. The transmission choices are held in a variant subsystem and are selected by either using the hyperlinks in the model or right-clicking the Transmission subsystem, selecting Variant -> Override using, and the desired variant.

Ports

Physical Signal

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Physical signal port that outputs the change in rotational power.

Conserving

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Mechanical rotational conserving port associated with the case.

Mechanical rotational conserving port associated with the load.

Mechanical rotational conserving port associated with driving source.

Parameters

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Option to measure the instantaneous power or an average power measurement.

  • Instantaneous power — Output the rotational power measured at the current simulation time step.

  • Average power over a specified period — Output the rotational power averaged over a fixed time period.

  • Average power over a vibration — Output the rotational power averaged over one vibration period.

  • Average power over a revolution — Output the rotational power averaged over one revolution period.

Time period that the block uses to compute the average power. For example, you can set this value to the cycle length of a rotating device.

Dependencies

To enable this parameter, set Measurement type to Average power over a specified period.

Highest vibration frequency to use to average the rotational power. Very high values can reduce simulation speed. Very low values can result in lower power measurements.

Dependencies

To enable this parameter, set Measurement type to Average power over a vibration.

Highest speed to use to average the rotational power. Very high values can reduce simulation speed. Very low values can result in lower power measurements.

Dependencies

To enable this parameter, set Measurement type to Average power over a revolution.

Extended Capabilities

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

Version History

Introduced in R2013a

See Also