Program controlled force measurement and control system
AssigneeTensor Development, Inc.
InventorJames L. McIntosh
Life of this patent
Estimating the term…
Abstract
A microprocessor based electric actuator control system is provided which allows accurate determination of the forces opposing movement of manipulator driveshaft. The control system electronically sets a predetermined current through an actuator to produce an electromagnetic force. A displacement measuring device, in conjunction with a time clock measures velocity and calculates acceleration of the actuator in response to the current. The force on the shaft is computer varied such that the acceleration is determined. For the acceleration to be zero, the electromagnetic force be exactly balanced by forces equal but opposite in magnitude. Since the force value is determined by the computer, the opposing force is also accurately determined with no external sensing device needed.
Claims25
A system for providing program controlled force in an apparatus, comprising:
- a driveshaft adapted for engagement with a load to perform a function by moving said driveshaft against said load;
- a direct current electric motor having an actuator connected to said driveshaft, said motor being operable in the current mode to control the force applied to the actuator thereof by varying the current through the windings;
- means mounted to said motor actuator for movement therewith for providing an output signal indicative of the position of said actuator with respect to a reference position;
- a clock for providing timing signals;
- an electrical power source;
- current regulator means connected between said power source and the windings of said motor;
- and
- processor means responsive to said output signals and to signals from said clock for controlling the output of said regulator and varying the current through the windings of said motor to provide a preprogrammed value of force exerted by the actuator of said motor and, thereby, the force exerted by said driveshaft against said load.
An improved variable force exerting system of the type which includes a force exerting member adapted for engagement with a load to effect movement thereof, means for connecting the force exerting member to the driveshaft of a DC motor in which the torque thereof is controlled by the current through the windings, wherein the improvement comprises:
- a current mode power supply connected to the windings of said DC motor, said power supply having means for controlling the positive and negative current produced thereby to change the direction and value of the current flow through the motor windings and vary the torque thereof and thereby change the force applied by the driveshaft to the force exerting member to effect movement of the load.
A method for determining the value of an unknown force of a load opposing movement of the driveshaft of an electric actuator of the type in which the force applied to the driveshaft is a linear function of the current through the actuator, comprising:
- supplying current to the actuator with a current mode controlled regulator having a plurality of discrete selectable current values;
- producing signals indicative of the direction and extent of the movement of the driveshaft of the actuator;
- providing regular periodic timing pulses;
- providing a program controlled processor for receiving said driveshaft movement signals and said timing pulses;
- periodically calculating with said processor the acceleration of the driveshaft from said driveshaft movement signals and said timing pulses;
- calibrating the actuator by calculating driveshaft acceleration values with no load and a known load for a plurality of discrete current values being supplied to the actuator to determine the force applied to a load by the driveshaft of the actuator for each of said discrete selectable current values from the regulator;
- and
- controlling said current regulator with said processor to vary the current supplied by the regulator to the actuator with the unknown load connected to the driveshaft thereof until the acceleration of the driveshaft is about zero and determining the value of the unknown force from the current value at that point.
A method for determining the value of an unknown force of a load opposing movement of the driveshaft of an electric actuator of the type in which the force applied to the driveshaft is a linear function of the current through the actuator, comprising:
- supplying current to the actuator with a current mode controlled regulator having a plurality of discrete selectable current values;
- producing signals indicative of the direction and extent of the movement of the driveshaft of the actuator;
- providing regular periodic timing pulses;
- periodically calculating from said driveshaft movement signals and said timing pulses the acceleration of the driveshaft;
- calibrating the actuator by calculating driveshaft acceleration values with a known load for a plurality of discrete motor temperature values with a selected current value being supplied to the actuator to determine the force applied to said known load by the driveshaft of the actuator for each of said discrete temperature values;
- and
- varying the current supplied by the regulator to the actuator with the unknown load connected to the driveshaft thereof until the acceleration of the driveshaft is about zero and determining the value of the unknown force from the current value at that point.
A method for determining the value of an unknown mass attached to the driveshaft of an electric actuator of the type in which the force applied to the driveshaft is a linear function of the current through the actuator, comprising:
- supplying current to the actuator with a current mode controlled regulator having a plurality of discrete selectable current values;
- producing signals indicative of the direction and extent of the movement of the driveshaft of the actuator;
- providing regular periodic timing pulses;
- providing a program controlled processor for receiving said driveshaft movement signals and said timing pulses;
- periodically calculating with said processor the acceleration of the driveshaft from said driveshaft movement signals and said timing pulses;
- calibrating the actuator by calculating driveshaft acceleration values with no load and a known load for a plurality of discrete current values being supplied to the actuator to determine the force applied to a load by the driveshaft of the actuator for each of said discrete selectable current values from the regulator;
- setting a selected value of current supplied by the regulator to the actuator with the unknown mass connected to the driveshaft thereof and measuring the acceleration of the driveshaft;
- and
- calculating the unknown mass from the measured value of acceleration and the force value applied to the shaft at the selected value of current set to be supplied by the regulator to the actuator.
A system for controlling the force applied to a load comprising:
- an electric actuator having a driveshaft connected to the load;
- encoder means for producing signals indicative of the direction and incremental value of movements in the driveshaft of said actuator;
- means for producing discrete selectable values of current connected to said actuator to produce a force on the driveshaft thereof proportional to the current value supplied;
- digital program controlled processor means connected to said encoder means for receiving signals therefrom and calculating values of driveshaft velocity and acceleration from incremental movement as a function of time and connected to said current producing means to select values of current based upon said calculated driveshaft velocity and acceleration values to control the force applied to the load by the driveshaft.
A system for providing program controlled force in an apparatus, comprising:
- a driveshaft adapted for engagement with a load to perform a function by moving said driveshaft against said load;
- a direct current electric motor having an actuator connected to said driveshaft, said motor having operable in the current mode to control the force applied to the actuator thereof by varying the current through the windings;
- means mounted to said motor actuator for movement therewith for providing an output signal indicative of the angular acceleration thereof;
- an electrical power source;
- current regulator means connected between said power source and the windings of said motor;
- and
- processor means responsive to said output signals for controlling the output of said regulator and varying the current through the windings of said motor to provide a preprogrammed value of force exerted by the actuator of said motor and, thereby, the force exerted by said driveshaft against said load.
Dependencies are inferred from the claim text.