Thermal stabilization of inertial measurement units

Patent metadata

Field	Value
Publication number	US-10845375-B2
Application number	US-201715420910-A
Country	US
Kind code	B2
Filing date	Jan 31, 2017
Priority date	Feb 19, 2016
Publication date	Nov 24, 2020
Grant date	Nov 24, 2020

Abstract

A thermal stabilization system stabilizes inertial measurement unit (IMU) performance by reducing or slowing operating variations over time of the internal temperature. More specifically, a thermoelectric heating/cooling device operates according to the Peltier effect, and uses thermal insulation and a mechanical assembly to thermally and mechanically couple the IMU to the thermoelectric device. The thermal stabilization system may minimize stress on the IMU and use a control system to stabilize internal IMU temperatures by judiciously and bidirectionally powering the thermoelectric heating/cooling device. The thermal stabilization system also may use compensation algorithms to reduce or counter residual IMU output errors from a variety of causes such as thermal gradients and imperfect colocation of the IMU temperature sensor with inertial sensors.

First claim

The invention claimed is:

1. A thermal stabilization system for stabilizing operation of an inertial measurement unit (IMU), the thermal stabilization system comprising:
a thermoelectric device for stabilizing the temperature around the IMU;
a controller configured to monitor a temperature around the thermoelectric device;
a drive circuit configured to generate a pulse width modulated (PWM) drive signal to power the thermoelectric device based on the monitored temperature;
the controller further configured to monitor a duty cycle of the generated PWM drive signal, the controller further configured to generate a control signal for controlling the drive circuit based on the monitored temperature and the monitored duty cycle of the generated PWM drive signal; and
the controller further configured to vary gain coefficients for the monitored duty cycle of the generated PWM drive signal to compensate for a dead-band in the generated PWM drive signal.

2. The thermal stabilization system of claim 1 , the controller further configured to increase loop gain coefficients for the control signal to compensate for a gain reduction that occurs when the monitored duty cycle of the generated PWM drive signal falls below a value dependent on at least one of a rise time and fall time of the generated PWM drive signal.

3. The thermal stabilization system of claim 1 , the controller further configured to adjust loop gain coefficients for the control signal to compensate for a dead-band response associated with transitioning the thermoelectric device between heating and cooling operations.

4. A thermal stabilization system for stabilizing operation of an inertial measurement unit (IMU), the thermal stabilization system comprising:
a thermoelectric device for stabilizing the temperature around the IMU;
a drive circuit generating a drive signal for operating the thermoelectric device; and
a controller monitoring a temperature around the thermoelectric device, the controller further monitoring a duty cycle for the generated drive signal used for operating the drive circuit, the controller generating a control signal for controlling the drive circuit based on the monitored temperature and the monitored duty cycle of the generated drive signal;
the controller further configured to adjust loop gain coefficients for the control signal to compensate for a dead-band response associated with transitioning the thermoelectric device between heating and cooling operations; and
the controller further configured to increase the loop gain coefficients by a correction factor inversely proportional to a most recent measurement of the monitored duty cycle of the generated drive signal.

5. The thermal stabilization system of claim 4 , the controller further configured to apply a scale factor compensation value to the monitored duty cycle of the generated drive signal to compensate for different efficiencies of the thermoelectric device during the heating and cooling operations.

6. The thermal stabilization system of claim 4 , the controller further configured to apply a dead-time compensation value to the monitored duty cycle of the generated drive signal to compensate for an increased duty cycle rate of change when the monitored duty cycle of the generated drive signal drops below a value dependent on at least one of a rise time and fall time of the generated drive signal.

7. The thermal stabilization system of claim 4 , wherein the IMU is held in compression by the thermoelectric device so the IMU operates in a linear operating region.

8. The thermal stabilization system of claim 1 , the controller further configured to change the gain coefficients by a correction factor that is based on a most recent measurement of the monitored duty cycle of the generated PWM drive signal.

9. The thermal stabilization system of claim 8 , wherein the correction factor is inversely proportional to the most recent measurement of the monitored duty cycle of the generated PWM drive signal.

10. The thermal stabilization system of claim 8 , the controller further configured to apply a scale factor compensation value to the monitored duty cycle of the generated PWM drive signal to compensate for different efficiencies of the thermoelectric device during the heating and cooling operations.

11. The thermal stabilization system of claim 8 , the controller further configured to apply a dead-time compensation value to the monitored duty cycle of the generated PWM drive signal to compensate for an increased duty cycle rate of change when the monitored duty cycle of the generated PWM drive signal drops below a value dependent on at least one of a rise time and fall time of the generated PWM drive signal.

12. The thermal stabilization system of claim 1 , wherein the IMU is held in compression by the thermoelectric device so the IMU operates in a linear operating region.

Assignees

• Agjunction Llc

Inventors

• Sommer Jeremy Sinclair

Classifications

• H10W76/138

  having another interconnection being formed by a cover plate parallel to the conductive base, e.g. sandwich type · CPC title

• G01C21/183

  Compensation of inertial measurements, e.g. for temperature effects · CPC title

• G05D23/1917 Primary

  using digital means · CPC title

• F25B21/04

  reversible · CPC title

• F25B2321/02

  using Peltier effects; using Nernst-Ettinghausen effects · CPC title