Linear actuator control structure

• US 6,614,195 B2
• Filed: 05/09/2001
• Issued: 09/02/2003
• Est. Priority Date: 05/09/2000
• Status: Expired

• Current Assignee: Tennant Company
• Original Assignee: Tennant Company
• Inventors: Milun, Richard, Haeg, John, Schwartz, Terry, Erko, Robert, Bushey, Bruce
• Primary Examiner(s): Ramirez, Nestor
• Assistant Examiner(s): JONES, JUDSON
• Application Number:
  US09/851,831
• Publication Number:
  US 20010054533A1
• Time in Patent Office: 846 Days
• Field of Search: 318/135, 318/254, 318/635, 318/636, 318/560, 318/561, 318/565, 318/595, 318/632, 318/621, 310/12, 310/15, 310/17, 310/19
• US Class Current: 318/135
• CPC Class Codes: A47L 11/4011 Regulation of the cleaning machine by electric means; Control systems and remote control systems therefor
• CPC Class Codes: A47L 11/4052 Movement of the tools or the like perpendicular to the cleaning surface
• CPC Class Codes: A47L 11/4063 Driving means; Transmission means therefor
• CPC Class Codes: A47L 11/4066 Propulsion of the whole machine
• CPC Class Codes: H02P 25/06 Linear motors

Abstract

A control system for a linear actuator having an electric motor drawing a variable current level during operation. The control system includes a current level sensor for determining an operational current level of the linear actuator and a controller for generating a drive signal and a force request signal representative of a desired current level of the linear actuator. The drive signal remains constant during a predetermined time interval of the controller. The control system further includes a current limiting component for receiving the force request signal, the current level of the linear actuator and the drive signal. The current limiting component minimizes the current level of the electric motor in response to a comparison between the force request signal and the desired current level within a time interval substantially smaller than the predetermined time interval of the controller.

Claims

1. A control system for a linear actuator having an associated current level, said control system comprising:

a current control component for controlling a current flow to the linear actuator, said current control component responsive to an input control signal;

a current sensing component for determining an operation current level of the linear actuator and generating a current signal as a function of the operational current level of the linear actuator;

a control device for generating a drive signal and a force request signal;

a load signal generating device responsive to the force request signal and the current signal; and

a control device for controlling the current control component, said control device accepting a load signal and the drive signal and generating the input control signal to control the current control component.

2. A control system for a linear actuator according to claim 1, wherein the current control component is a switch device for operatively coupling the linear actuator to a circuit ground.

3. A control system for a linear actuator according to claim 2, wherein the switch device includes a FET switch.

4. A control system for a linear actuator according to claim 1, wherein the linear actuator current signal detection component includes a shunt resistor structure.

5. A control system for a linear actuator according to claim 1, wherein the force request signal is a digital signal.

6. A control system for a linear actuator according to claim 1, wherein the force request signal operation component includes a digital-to-analog converter.

7. A control system for a linear actuator according to claim 1, wherein the load signal generating device is a comparator for comparing the force request signal and the current signal.

8. A linear actuator control system comprising:

a linear actuator having a predetermined current level;

a current level detection device operatively coupled to the linear actuator and generating a current level signal;

a digital control device generating a first control signal and a second control signal, said digital control device receiving a feedback signal;

a comparator device for receiving the first control signal and the current level signal, said comparator device generating a comparison signal; and

a control device accepting the comparison signal and the second control signal and controlling the current level of the linear actuator.

9. A linear actuator control system according to claim 8, wherein the control device includes a FET switch.

10. A linear actuator control system according to claim 8, wherein the control device includes a NAND logic device.

11. A linear actuator control system according to claim 8, wherein the current level detection device includes a shunt resistor structure.

12. A linear actuator control system according to claim 8, wherein the first and second control signals are digital signals.

13. A linear actuator control system according to claim 8, first control signal is processed by a D/A converter prior to being introduced to the comparator device.

14. A control system for a linear actuator device comprising:

a linear actuator including an electric motor having a current level;

an electronic controller generating a pair of signals, each signal representative of a desired delivery of current to the linear actuator;

a motor current sensing device for determining the current level of the linear actuator electric motor;

said device generating a current signal;

a comparator for comparing the current signal to one of the pair of signals, said comparator generating a comparator signal upon the current signal exceeding a current level associated with the one of the pair of signals;

a logic device receiving the comparator signal and the other of the pair of signals, said logic device controlling the flow of current to the electric motor of the actuator.

15. A control system according to claim 14, wherein the logic device is a NAND device and wherein an output of the NAND device is coupled to a current switch.

16. A control system according to claim 15, wherein the current switch is a FET switch.

17. A control system according to claim 14, wherein the electronic controller operates at a predetermined system speed, and wherein the pair of signals are generated and held through a predetermined time interval dependent upon the system speed.

18. A control system of claim 17, wherein the motor current sensing device, the first comparator, and the logic device function to control a current flow to the electric motor within a time interval which is substantially smaller than the predetermined time interval of the electronic controller.

19. A control system for a linear actuator comprising:

a linear actuator having an electric motor, said electric motor drawing a variable current level during operation;

a current level sensor for determining an operational current level of the linear actuator;

a controller for generating a drive signal, said drive signal remaining constant during a predetermined time interval, said controller further generating a force request signal representative of a desired current level of the linear actuator; and

a current limiting component for receiving the force request signal, the current level of the linear actuator and the drive signal, said current limiting component minimizing the current level of the electric motor in response to a comparison between the force request signal and the desired current level, said current limiting component minimizing the current level within a time interval substantially smaller than the predetermined time interval.

20. A control system according to claim 19, wherein the current limiting component includes a comparator and a logic device.

21. A control system according to claim 20, wherein the drive signal includes a digital signal and the force signal includes an analog signal.