Digital robot control having an improved current sensing system for power amplifiers in a digital robot control

Claim 5

A system as set forth in claim 2 wherein: the motor is a brush type DC motor; said bridge circuit in an H type bridge having four legs with a cross path in which the motor is connected; one of said switches is connected in each bridge leg with an upper leg and the opposite lower leg forming a forward path to drive the motor in the forward direction and with the other opposite upper and lower legs forming a reverse path to drive the motor in the reverse direction; one of said switches in each motor path has a control signal applied thereto to control the drive current conduction time; and the other of said switches in each motor path has a control signal applied thereto to make it nonconductive when the one drive current controlling switch on its side of the H bridge is conductive and during underlap time and to make it conductive for the rest of the time in each cycle so as to provide paths for freewheeling motor currents.

Claim 6

A system as set forth in claim 2 wherein: the motor is a brushless DC motor using the central resistance means for sensing the average motor current therein.

Claim 7

A system as set forth in claim 1 wherein: said digital control means includes velocity and position control loop means generating a motor drive current command; said digital control means further includes torque control loop means responding to said motor drive current command and said motor current sample signals to generate voltage commands; pulse width modulator means for generating, said power switch control signals from said voltage commands; said current feedback signals being coupled to said torque control loop.

Claim 8

A robot having: an arm with a plurality of joints; each of said joints having an electric drive motor associated therewith; each of said motors coupled to a power amplifier including a bridge circuit with a plurality of legs each having one end thereof connected to supply drive current to the motor from a power supply connected across said bridge circuit to the other ends of said legs; a semiconductor switch having a control terminal, one said switch being connected in each bridge leg to make that leg to be conductive when a control signal is applied to said switch control terminal; resistance means adapted for central sampling, serially connected between said bridge circuit and the power supply, independent of the number of legs in the plural leg bridge circuit; digital control means for cyclically generating patterns of switch control signals that are pulse width modulated to operate said power switches and produce motor drive current having direction and magnitude required by cyclically generated robot drive control commands; means for cyclically sampling the current through said resistance means at a predetermined time interval, during the patterns of semiconductor switch conduction in each controlled cycle of the motor supply path, in synchronism with the digital control means cycle and within said short cycle portion; said digital control means generating the patterns of said switch control signals to force each motor supply path through said bridge circuit to be conductive over at least a short portion of each control cycle, the direction of the current through the motor adapted to be sampled, the sampled current through the resistance means flowing therethrough, at a time when it accurately indicates the polarity and average of the current flowing in the motor; said sampling means coupling signals representing the current samples to said digital control means to provide feedback control over the generation of said robot drive control commands; one of said power amplifiers with its resistance means and current sample coupling means being provided for each joint motor; and said digital control means generating switch control signals for switches in each of said power amplifiers.

Claim 9

A robot having: an arm with a plurality of joints; each of said joints having an electric drive motor associated therewith; each of said motors coupled to a power amplifier including a bridge circuit with a plurality of legs each having one end thereof connected to supply drive current to the motor from a power supply connected across said bridge circuit to the other ends of said legs; a semiconductor switch having a control terminal, one said switch being connected in each bridge leg to make that leg to be conductive when a control signal is applied to said switch control terminal; resistance means adapted for central sampling, serially connected between said bridge circuit and the power supply, independent of the number of legs in the plural leg bridge circuit; digital control means for cyclically generating patterns of switch control signals that are pulse width modulated to operate said power switches and produce motor drive current having direction and magnitude required by cyclically generated robot drive control commands; means for cyclically sampling the current through said resistance means at a predetermined time interval, during the patterns of semiconductor switch conduction in each controlled cycle of the motor supply path, in synchronism with the digital control means cycle and within said short cycle portion; said digital control means generating the patterns of said switch control signals to force each motor supply path through said bridge circuit to be conductive over at least a short portion of each control cycle, the direction of the current through the motor adapted to be sampled, the sampled current through the resistance means flowing therethrough, at a time when it accurately indicates the polarity and average of the current flowing in the motor; said sampling means coupling signals representing the current samples to said digital control means to provide feedback control over the generation of said robot drive control commands; one of said power amplifiers with its resistance means and current sample coupling means being provided for each joint motor; and said digital control means generating switch control signals for switches in each of said power amplifiers.

Claim 10

A system as set forth in claim 3 wherein: said bridge circuit is enclosed in a power block; said power block is provided with external power terminals for connection to the power supply and external terminals for coupling of the switch control signals to said power switch control terminals; and said resistance means is connected between one of said external power terminals of said power block and one output end of the power supply.

Claim 11

A system as set forth in claim 4 wherein: said bridge circuit is enclosed in a power block; said power block is provided with external power terminals for connection to the power supply and external terminals for coupling of the switch control signals to said power switch control terminals; and said resistance means is connected between one of said power terminals and one input end of the power supply.

Claim 12

A system as set forth in claim 7 wherein: the voltage drop across said resistance means is coupled to said digital control means to represent the current samplings.

Claim 13

A system as set forth in claim 8 wherein: the voltage drop across said resistance means is coupled to said digital control means to represent the current samplings.

Claim 14

A system as set forth in claim 1 wherein: said digital control means generates an up/down counter ramp as a function of time; said digital control means further generates said switch control signals to force motor path conduction in one direction during a short control cycle portion about one end of the ramp and in the opposite direction during a short control cycle portion about the other end of the ramp; and said cyclical means samples the resistance means current at the midpoint of the forced conduction time periods.

Claim 15

A system as set forth in claim 1 wherein the motor is a DC brush type and the bridge circuit is an H-bridge type enclosed in a power block.

Claim 16

A system as set forth in claim 1 wherein the motor is a brushless DC type and the bridge circuit is internally configured and enclosed in a power block to energize three motor phase windings in rotating pairs.