Missile servo actuation system and method of controlling a servo actuation system in a missile

1 . A method of controlling a servo actuation system in a missile, the method comprising the steps of:

estimating a temperature of a motor comprised in the servo actuation system from a plurality of motor parameters including at least one of a motor resistance or a torque constant;

wherein the at least one of the motor resistance or the torque constant are estimated by:

introducing high frequency current pulses;

measuring motor current;

estimating motor voltage and motor velocity; and

determining using a recursive least squares algorithm the at least one of the motor resistance or the torque constant based on the motor current measured, the motor voltage and the motor velocity estimated;

estimating motor inertia and friction from the estimated motor temperature from the plurality of motor parameters; and

controlling the motor in the missile based at least in part on the estimated motor temperature to maintain target performance criteria for current, velocity and position when the estimated motor temperature is less than a temperature threshold and the estimated motor temperature has changed from a prior estimated motor temperature,

wherein the high frequency current pulses are arranged to have negligible effect on a motor torque or a motor acceleration.

2 . A method according to claim 1 , wherein the step of estimating a temperature of a motor includes comparing the plurality of motor parameters with known values at a reference temperature.

3 . A method according to claim 1 , wherein the step of estimating motor voltage includes determining a demanded voltage and compensating for the effects of inverter deadband.

4 . A method according to claim 1 , wherein the step of estimating a temperature of a motor comprises weighting the plurality of motor parameters.

5 . A method according to claim 1 , wherein the controlling the motor in the missile based at least in part on the estimated motor temperature to maintain target performance criteria for current, velocity and position comprises generating a control signal using one or more control algorithms, wherein the one or more control algorithms include a gain-scheduling algorithm, and wherein the gains are dynamically adjusted to maintain the target performance criteria for current, velocity and position.

6 . A method according to claim 1 , wherein the controlling the motor in the missile based at least in part on the estimated motor temperature to maintain target performance criteria for current, velocity and position comprises generating a control signal using one or more control algorithms, wherein the one or more control algorithms include a cut-off function, such that the motor is disabled when the estimated motor temperature exceeds the temperature threshold.

7 . A method according to claim 4 , wherein the weights dynamically change based on a characteristic of each of the plurality of motor parameters as determined by a range of change or rate of change of each during a measurement.

8 . A servo actuation system in a missile, the system comprising:

a motor configured to control a mechanical component in the missile;

a controller;

a parameter estimator comprising a comparator, a first estimator and a second estimator, the parameter estimator configured to estimate motor temperature in the missile from a plurality of motor parameters including a motor resistance and a torque constant, the parameter estimator including the first estimator configured to estimate the motor resistance and the torque constant by:

introducing high frequency current pulses;

measuring motor current;

estimating motor voltage and motor velocity; and

determining using a recursive least squares algorithm the motor resistance and the torque constant based on the motor current measured, the motor voltage and the motor velocity estimated, wherein the motor temperature is inferred by the comparator from the estimated motor resistance and torque constant and the second estimator is configured to estimate motor inertia and friction from the inferred motor temperature,

wherein the high frequency current pulses are arranged to have negligible effect on a motor torque or a motor acceleration.

9 . A servo actuation system according to claim 8 , wherein the controller is configured to control the motor in the missile based at least in part on the estimated motor temperature to maintain target performance criteria for current, velocity and position when the estimated motor temperature is less than a temperature threshold and the estimated motor temperature has changed from a prior estimated motor temperature.

10 . A servo actuation system according to claim 9 , wherein the mechanical component is selected from a group consisting of a wing, tail fin and fuel pump.

11 . A servo actuation system according to claim 8 , wherein the first estimator is configured to dynamically weight the plurality of motor parameters in estimating the motor temperature.