Stepper Motor Winding Current Control via XOR Gates
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Solution Overview
Problem
Existing stepper motor drive systems accelerate and decelerate both actual and parasitic moments of inertia, leading to excessive torque production, particularly during acceleration, and struggle with varying load torques, resulting in slow control characteristics and potential rotor oscillations due to simultaneous current supply and control of both motor windings.
Innovation Solution
A circuit arrangement with separate XOR gates and diodes for each motor winding allows for independent control of current flow time based on encoder and phase signals, reducing current supply in the winding anticipating the next reversal, thereby reducing torque production in low-load conditions and preventing oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If current supply is controlled simultaneously in both motor windings using a single current-controlling signal, then the control circuit is simple, but the control characteristics become slow and rotor oscillations occur
Solution Approach 1:
The patent divides the control of current supply into separate control paths for each motor winding. Instead of using a single current-controlling signal for both windings, the invention implements independent control circuits that can adjust current flow time for winding A and winding B separately, thereby improving control response speed and preventing rotor oscillations.
Solution Approach 2:
The patent introduces dynamic adjustment of current flow time based on the relationship between encoder signals and phase signals. The control system dynamically modifies the energization duration of each winding according to real-time motor position and speed conditions, enabling adaptive control that responds quickly to changing load conditions without causing oscillations.
2Reliability
If integration element with finite time constant is used to control current amplitude, then the control is stable, but the control characteristics are slow and require motor- and load-adapted dimensioning
Solution Approach 1:
The patent changes the control parameter from current amplitude (which requires integration with fixed time constants) to current flow time (pulse width modulation). This allows the control system to adjust motor torque by varying the duration of current pulses rather than their amplitude, eliminating the need for integration elements with motor-specific time constants and improving adaptability across different motor and load configurations.
Solution Approach 2:
The patent removes the integration element from the control circuit entirely. Instead of using an integrator to control current amplitude over time, the invention extracts the time-control function and applies it directly to the current switch-on duration, simplifying the circuit and improving response speed while maintaining stable control.
3Force
If current amplitude is reduced in both motor windings simultaneously, then the torque is reduced for low-load conditions, but the control is not optimized for preventing oscillations in specific windings
Solution Approach 1:
The patent applies different current control strategies to different motor windings based on their specific roles in the motor cycle. By controlling the current flow time independently for each winding, the system can optimize torque production in one winding while preventing oscillations in the other, achieving local optimization that improves overall motor performance and stability.
Data Source
AI summary
A circuit arrangement for automatic, load-dependent control of at least one winding current of a respective motor winding of a self-timed bipolar stepper motor, includes a first power driver circuit for a first motor winding and a second power driver circuit for a second motor winding. The circuit arrangement includes a first XOR gate and a second XOR gate, and a first resistor connected so as to couple the first XOR gate to an anode of a first diode. A cathode of the first diode is coupled to the comparator input of the first power driver circuit via a second resistor. A third resistor is connected so as to couple the second XOR gate to an anode of a second diode. A cathode of the second diode is coupled to the current-controlling comparator input of the second power driver circuit via a fourth resistor.