# US 5,703,424 A · Bias current control circuit

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 5,703,424 A
- Document ID: US5703424A
- Status: Granted
- Kind: A
- Application number: 08/714,246
- Filed: 1996-09-16
- Granted: 1997-12-30
- Earliest claimed: 1996-09-16
- Assignees: Mechanical Technology Incorporated
- Inventors: Richard A. Dorman
- Web page: https://patentgrep.com/patent/US5703424A

## CPC

- F16C 32/0451: {Details of controllers, i.e. the units determining the power to be supplied, e.g. comparing elements, feedback arrangements with P.I.D. control}
- F16C: SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS

## Abstract

A control system for a magnetic bearing includes a sensor which generates an output representative of the relative shaft position. The signal from the sensor is processed by an integrator and offset adjustment block and a difference amplifier to subtract the processed sensor signal from a reference voltage. The difference signal result is fed to a bias control circuit including voltage dividers which generates a voltage which is received by coil current power amplifiers for both the upper and lower magnetic coils. Coil currents are then generated to stabilize the magnetic bearing.

## Claims

### Claim 1

A control system for a magnetic bearing, the magnetic bearing including a rotor responsive to a shaft and a stator including upper and lower magnetic coils, the control system including:
sensor means for determining a relative position of the shaft;
means for integrating and offsetting said relative position of the shaft;
means for subtracting an output of said means for integrating and offsetting from a reference voltage;
bias current control means responsive to said means for subtracting, said bias current control means including voltage dividers which generate a voltage output;
coil current amplifier means receiving said voltage output from said bias current control means, said coil current amplifier means generating a current to the upper and lower coils of the magnetic bearing.

### Claim 2 (depends on 1)

The control system of claim 1 wherein said means for integrating and offsetting includes a time constant of approximately one second.

### Claim 3 (depends on 1)

The control system of claim 1 wherein the means for integrating and offsetting further includes means for setting an integrator gain.

### Claim 4 (depends on 3)

The control system of claim 3 wherein said means for integrating and offsetting further includes means for setting bearing static stiffness.

### Claim 5 (depends on 4)

The control system of claim 4 wherein said means for integrating and offsetting further includes means for setting bearing dynamic stability.

### Claim 6 (depends on 1)

The control system of claim 1 further including frequency dependent filters for filtering output from said sensor means.

### Claim 7 (depends on 1)

The control system of claim 1 wherein said coil current amplifier means includes an upper coil amplifier for providing current to said upper magnetic coil and a lower coil amplifier for providing current to said lower magnetic coil, and wherein said bias current control means, in response to a change in output of said sensor means, effects a simultaneous change in output of said upper and lower coil amplifiers which is directly proportional to the change in the change in output of said sensor means.

### Claim 8 (depends on 4)

The control system of claim 4 wherein said means for setting bearing static stiffness includes proportional and gain set amplifying means.

### Claim 9 (depends on 5)

The control system of claim 5 wherein said means for setting bearing dynamic stability includes differentiating and gain set amplifying means.