Method and apparatus for controlling a servo motor using a stepper motor controller integrated circuit
First Claim
1. A method for controlling a servo motor, said method comprising:
- (a) providing (i) a stepper motor controller integrated circuit, (ii) a DC servo motor that rotates in two directions, (iii) a pulse-width modulated speed control signal, (iv) a direction control signal, and (v) an interface circuit;
(b) applying said direction control signal to a Phase control input of said stepper motor controller integrated circuit such that;
a first logic state of said direction control signal tends to cause said DC servo motor to rotate in a forward direction, and a second logic state of said direction control signal tends to cause said DC servo motor to rotate in a reverse direction;
(c) applying said speed control signal to said interface circuit which generates (i) a comparator signal that is provided to a Comparator input of said stepper motor controller integrated circuit, and (ii) a trigger signal that is provided to a Pulse Time input of said stepper motor controller integrated circuit, said speed control signal generating pulses at times that said DC servo motor is to rotate in either direction; and
(d) applying an output signal that is generated by said stepper motor controller integrated circuit to said DC servo motor at times that said DC servo motor is to rotate in either direction, said output signal having a duty cycle of pulses related to a duty cycle of said speed control signal.
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Accused Products
Abstract
An improved DC servo motor driver circuit is provided that is based upon a readily available conventional stepper motor driver integrated circuit (IC). The IC'"'"'s current "Sense" line that is usually connected to a low value resistor is instead tied to DC common or to ground. The IC'"'"'s "Comparator" input, which is usually connected to the current Sense line, is connected to a pulsing input signal that provides the comparators with an appropriate voltage to make the comparators believe that more current is required at the very times the remaining portions of the circuit are attempting to provide current to the DC servo motor. An RC circuit is provided at the IC'"'"'s "Pulse Time" input so that the monostable timer is properly triggered. An ASIC provides the proper logic signals to not only control the direction of the DC servo motor, but also to provide pulses of an appropriate frequency and duty cycle to emulate a pulse-width modulator. The direction signal is connected to the "Phase" input, and the pulse-width modulated signal is provided to interface circuitry that drives the Comparator and Pulse Time inputs. The output transistors in an H-bridge driver stage within the stepper motor driver IC are controlled so as to provide pulse-width modulated voltage pulses across the motor winding of the DC servo motor, such that this DC servo motor can operate exactly as if it were being driven by an integrated circuit that was specifically designed to act as a DC servo motor driver circuit. The average current supplied over time to the DC servo motor is directly related to the duty cycle of the pulse-width modulated voltage pulses across its winding, which in turn is directly related to the duty cycle of the main input control signal.
55 Citations
25 Claims
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1. A method for controlling a servo motor, said method comprising:
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(a) providing (i) a stepper motor controller integrated circuit, (ii) a DC servo motor that rotates in two directions, (iii) a pulse-width modulated speed control signal, (iv) a direction control signal, and (v) an interface circuit; (b) applying said direction control signal to a Phase control input of said stepper motor controller integrated circuit such that;
a first logic state of said direction control signal tends to cause said DC servo motor to rotate in a forward direction, and a second logic state of said direction control signal tends to cause said DC servo motor to rotate in a reverse direction;(c) applying said speed control signal to said interface circuit which generates (i) a comparator signal that is provided to a Comparator input of said stepper motor controller integrated circuit, and (ii) a trigger signal that is provided to a Pulse Time input of said stepper motor controller integrated circuit, said speed control signal generating pulses at times that said DC servo motor is to rotate in either direction; and (d) applying an output signal that is generated by said stepper motor controller integrated circuit to said DC servo motor at times that said DC servo motor is to rotate in either direction, said output signal having a duty cycle of pulses related to a duty cycle of said speed control signal. - View Dependent Claims (2, 3, 4)
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5. A method for controlling a servo motor, said method comprising:
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(a) providing (i) a stepper motor controller integrated circuit, (ii) a DC servo motor that rotates in two directions, (iii) a direction control signal, (iv) a comparator signal, and (v) a trigger signal; (b) rotating said DC servo motor in a forward direction by applying said direction control signal at a first logic state to a Phase control input of said stepper motor controller integrated circuit, applying said trigger signal as a series of pulses to a Pulse Time input of said stepper motor controller integrated circuit, and applying said comparator signal as a series of pulses to a Comparator input of said stepper motor controller integrated circuit, wherein (i) a leading pulse edge of said comparator signal is substantially synchronized with a leading pulse edge of said trigger signal, (ii) a trailing pulse edge of said comparator signal occurs after a trailing edge of said trigger signal, and (iii) during the time between its leading and trailing edges, said comparator signal exhibits a voltage level so as to call for more current to be output from said stepper motor controller integrated circuit to said DC servo motor; and (c) rotating said DC servo motor in a reverse direction by applying said direction control signal at a second logic state to a Phase control input of said stepper motor controller integrated circuit, applying said trigger signal as a series of pulses to a Pulse Time input of said stepper motor controller integrated circuit, and applying said comparator signal as a series of pulses to a Comparator input of said stepper motor controller integrated circuit, wherein (i) a leading pulse edge of said comparator signal is substantially synchronized with a leading pulse edge of said trigger signal, (ii) a trailing pulse edge of said comparator signal occurs after a trailing edge of said trigger signal, and (iii) during the time between its leading and trailing edges, said comparator signal exhibits a voltage level so as to call for more current to be output from said stepper motor controller integrated circuit to said DC servo motor. - View Dependent Claims (6, 7, 8)
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9. A servo motor control circuit, comprising:
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(a) a logic circuit that generates;
(i) a pulse-width modulated speed control signal and (ii) a direction control signal;(b) an interface circuit that receives said speed control signal and generates;
(i) a comparator signal, and (ii) a trigger signal;(c) a stepper motor controller integrated circuit, having;
(i) a Phase input that receives said direction control signal, (ii) a Comparator input that receives said comparator signal, (iii) a Pulse Time input that receives said trigger signal, (iv) a motor drive output signal, and (v) a timer circuit;(d) said logic circuit being configured;
(i) to generate electrical pulses on said speed control signal at times when said motor drive output signal is to output current, a duty cycle of said speed control signal being related to the average amount of current that is to be output over time, and (ii) to place said direction control signal into a first logic state or a second logic state, relating to the direction of current flow that is to be output at said motor drive output signal; and(e) said interface circuit being configured;
(i) to generate said comparator signal having a value that causes said stepper motor controller integrated circuit to generate current at said motor drive output signal at times when said logic circuit generates electrical pulses on said speed control signal, and (ii) to generate a trigger signal having a value that causes said stepper motor controller integrated circuit to enable its timer circuit and thereby allow output current to flow at said motor drive output signal;said motor drive output signal having a duty cycle of pulses related to said duty cycle of said speed control signal. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A servo motor control circuit, comprising:
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(a) a logic circuit that generates;
(i) a pulse-width modulated speed control signal that provides pulses at times when it is desired to generate an output current of a motor drive output signal, and (ii) a direction control signal that is placed into one of a first logic state and a second logic state, relating to the direction of current flow of said motor drive output signal;(b) an interface circuit that receives said speed control signal and generates;
(i) a comparator signal, and (ii) a trigger signal;(c) a motor controller circuit comprising;
(i) a comparator, (ii) a timer circuit, (iii) a direction logic circuit, (iv) a forward direction driver, (v) a reverse direction driver, (vi) a plurality of output switching devices that generate said motor drive output signal, (vii) a Phase input that communicates said direction control signal to said direction logic circuit, (viii) a Comparator input that communicates said comparator signal to said comparator, and (ix) a Pulse Time input that communicates said trigger signal to said timer circuit;
said comparator outputting a signal to one of said forward direction driver and said reverse direction driver; and
said timer circuit outputting a signal to one of said forward direction driver and said reverse direction driver;(d) said motor controller circuit and said interface circuit being configured to; (i) generate a pulse output at said motor drive output signal in a forward direction when;
(A) said direction logic circuit receives said direction control signal at said Phase input having a first logic state, (B) said Comparator input receives said comparator signal having a first logic state that causes said comparator to output a signal to said forward direction driver, (C) said Pulse Time input receives said trigger signal as a pulse that causes said timer circuit to output a signal to said forward direction driver, (D) said direction logic circuit outputs a signal that allows current to flow through at least one of said plurality of output switching devices, (E) said forward direction driver outputs a signal that allows current to flow through at least one other of said plurality of output switching devices, thereby allowing current of said motor driver output signal to flow in a forward direction; and(ii) generate a pulse output at said motor drive output signal in a reverse direction when;
(A) said direction logic circuit receives said direction control signal at said Phase input having a second logic state, (B) said Comparator input receives said comparator signal having a first logic state that causes said comparator to output a signal to said reverse direction driver, (C) said Pulse Time input receives said trigger signal as a pulse that causes said timer circuit to output a signal to said reverse direction driver, (D) said direction logic circuit outputs a signal that allows current to flow through at least one of said plurality of output switching devices, (E) said reverse direction driver outputs a signal that allows current to flow through at least one other of said plurality of output switching devices, thereby allowing of at said motor driver output signal to flow in a reverse direction;and wherein said motor drive output signal exhibits a duty cycle of pulses related to a duty cycle of said speed control signal. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25)
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Specification