Control of stepping motors
First Claim
1. A closed loop control circuit for a stepping motor comprising:
- drive means having a plurality of switching positions in each of which the drive means is arranged to supply current to selected windings of a stepping motor in selected directions,means arranged to change the switching positions in sequence,sensor means arranged to generate a train of pulses representative of the speed and position of the motor, andcontrol means arranged to receive said train of pulses and to generate in response thereto change excitation signals for application to said drive means to change the switching positions,the control means being arranged to produce direction signals for application to said drive means to determine the direction in which the sequence of switching positions is changed, andsaid control means being arranged to generate a change excitation signal each time a selected number of said pulses is received, and wherein said selected number is variable whereby the time between successive change excitation signals is variable.
1 Assignment
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Accused Products
Abstract
A control circuit for a stepping motor (20) comprises a transistorised drive circuit (122) having a plurality of switching positions in each of which the drive circuit (122) is arranged to supply current to selected windings of the stepping motor in selected directions. A sequencer (130) is arranged to apply control signals to the drive circuit (122) to change the switching positions in sequence. An encoder (128) provides a train of pulses representative of the speed and position of the motor (120). An excitation controller (134) is arranged to receive the encoder pulses and to generate in response thereto change excitation signals for causing change of the switching positions, and change direction signals for determining the direction in which the sequence of switching positions is changed. The provision of both change excitation signals and direction signals offers maximum flexibility, because it enables, for example, speedy reversal of the torque of the stepping motor (120) by causing the sequencer (130) to step backwardly through the switching sequence. The change excitation signals are generated by said excitation controller (134) in a manner which enables the switching angle of the stepping motor to be varied substantially without limit so that complete control of the stepping motor is available.
21 Citations
15 Claims
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1. A closed loop control circuit for a stepping motor comprising:
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drive means having a plurality of switching positions in each of which the drive means is arranged to supply current to selected windings of a stepping motor in selected directions, means arranged to change the switching positions in sequence, sensor means arranged to generate a train of pulses representative of the speed and position of the motor, and control means arranged to receive said train of pulses and to generate in response thereto change excitation signals for application to said drive means to change the switching positions, the control means being arranged to produce direction signals for application to said drive means to determine the direction in which the sequence of switching positions is changed, and said control means being arranged to generate a change excitation signal each time a selected number of said pulses is received, and wherein said selected number is variable whereby the time between successive change excitation signals is variable. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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2. A control circuit for a stepping motor comprising:
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drive means having a plurality of switching positions in each of which the drive means is arranged to supply current to selected windings of a stepping motor in selected directions, means arranged to change the switching positions in sequence, sensor means for providing information relating to the speed and position of the motor, and control means arranged to receive the speed and position information and to generate in response thereto control signals for said drive means, wherein said control means includes inhibiting means arranged selectively to inhibit the application of control signals to said drive means. - View Dependent Claims (4)
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3. A control circuit for a stepping motor comprising:
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drive means having a plurality of switching positions in each of which the drive means is arranged to supply current to selected windings of a stepping motor in selected directions, means arranged to change the switching positions in sequence, sensor means for providing information relating to the speed and position of the motor, and control means arranged to receive the speed and position information and to generate in response thereto control signals for said drive means, wherein said control means includes step complete signal generating means arranged to generate a step complete signal upon receipt of information from said sensor means indicating the motor has moved a predetermined number of steps, and synchronizing means receiving said step complete signals and arranged to enable generation of said control signals upon receipt of a step complete signal.
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15. A closed loop torque-enhancing control circuit for a stepping motor having plural electrical windings and a rotatable shaft, said control circuit comprising:
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a rotational sensor coupled to the stepping motor and providing electrical pulse signals representing the rotational speed and position of the motor shaft; an electrical sequential switching circuit coupled to said sensor and successively providing electrical drive power to windings of the stepping motor at switch angles which are in advance of reaching a corresponding motor shaft equilibrium position and in response to successively counted numbers of said pulse signals; and a torque-enhancing switch angle control circuit coupled to said sensor and to said switching circuit which changes the magnitude of said advanced switching angle in proportion to the shaft speed of the motor thereby increasing the torque provided by the motor shaft.
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Specification