Motor Deceleration Control with Duty Limiting Against Overcurrent
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Solution Overview
Problem
Conventional motor control devices face the risk of overcurrent due to induced electromotive force during deceleration control, particularly when the duty at the start of deceleration is set to −100%, leading to potential overcurrent issues.
Innovation Solution
A motor control device with a drive circuit and a control unit that includes a current limit part to calculate and correct the duty limit value, ensuring the duty ratio does not exceed safe limits during deceleration, thereby preventing overcurrent by adjusting the energization of the coil based on the motor rotation speed and battery voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the duty at the start of deceleration control is set to -100%, then the motor deceleration performance is improved, but overcurrent occurs due to induced electromotive force
Solution Approach 1:
The control unit performs preliminary action by setting an initial duty value that is lower than the maximum absolute value before deceleration control begins. This preliminary setting prevents the induced electromotive force from causing overcurrent while still enabling effective deceleration, thereby resolving the contradiction between deceleration performance and overcurrent prevention
Solution Approach 2:
The duty value is made dynamic rather than fixed at -100%. The control unit adjusts the duty value based on the motor's rotational speed and induced electromotive force conditions, allowing the duty to vary during deceleration. This dynamic adjustment maintains optimal deceleration performance while preventing overcurrent by reducing duty when induced electromotive force becomes excessive
2Object-affected harmful factors
If the duty ratio is limited to prevent overcurrent, then overcurrent is suppressed, but the motor may not stop at the target position accurately
Solution Approach 1:
The control unit employs feedback by continuously monitoring the motor's rotational speed and the induced electromotive force during deceleration. Based on this feedback, the duty value is adjusted in real-time to prevent overcurrent while ensuring the motor reaches the target position. The feedback mechanism allows the system to maintain positioning accuracy despite duty limitations by making precise, adaptive adjustments
Solution Approach 2:
The duty ratio parameter is changed dynamically during deceleration control rather than maintaining a fixed limited value. The control unit modifies the duty parameter based on the motor's state, allowing the system to achieve both overcurrent suppression and accurate positioning by adapting the duty parameter to the specific operational conditions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively suppresses overcurrent during deceleration control by limiting the duty ratio, ensuring the motor stops at a target position while maintaining the coil current within a safe range, thus preventing damage to the drive circuit.
Implementation Method 1
a motor (10) having a coil (11)
Implementation Method 2
there is a risk of overcurrent due to an induced electromotive force
Data Source
AI summary
A motor control device controls a drive of a motor having a coil, and includes a drive circuit and a control unit. The drive circuit has a plurality of switching elements, and switches the energization of the coil. The control unit includes an energization control part and a current limit part. The energization control part accelerates and then decelerates the motor, and controls energization of the coil so that a rotation position of the motor stops at a target rotation position. The current limit part limits the current during a deceleration control.