Electric Tool Braking Control for Voltage Jumping and Reaction
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Solution Overview
Problem
Electric tools with braking functions face issues of increased reaction and voltage jumping due to regenerated energy, which can lead to loosening of the wheel nut and risk of exceeding the withstand voltage of elements, particularly when using PWM control for braking.
Innovation Solution
An electric tool with a controller that performs a first braking control by continuously turning on a predetermined switching element of the inverter circuit and switches to a second braking control of repeatedly turning on and off the same element, setting a duty ratio to manage voltage and reduce reaction, with a capacitor to absorb regenerated energy without exceeding its withstand voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If PWM control is used for braking, then reaction is reduced and wheel nut loosening is suppressed, but voltage jumps up due to regenerated energy and risk of exceeding withstand voltage increases
Solution Approach 1:
The braking control is divided into two distinct phases: first braking control and second braking control. The first phase uses continuous switching element on-state for strong braking force, while the second phase uses PWM control for voltage management. This segmentation allows each phase to optimize for its specific function without compromising the other.
Solution Approach 2:
The first braking control is executed preliminarily to reduce the motor rotation speed to a predetermined level before switching to the second braking control. This preliminary action removes the bulk of kinetic energy through continuous braking, making the subsequent PWM-based voltage management more effective and stable.
2Reliability
If first braking control is used, then voltage jumping is suppressed, but reaction increases and wheel nut may loosen
Solution Approach 1:
The braking process is segmented into two phases with distinct control strategies. The first phase handles voltage stability through continuous switching element activation, while the second phase handles reaction force reduction through PWM control. This segmentation ensures both voltage stability and low reaction force are achieved at different stages.
Solution Approach 2:
The control method employs periodic action by switching between two different braking control modes. The first braking control operates continuously until the rotation speed threshold is reached, then transitions to periodic PWM control in the second phase. This periodic transition optimizes both voltage management and reaction force control.
3Power
If continuously turning on switching elements, then braking force is strong, but reaction increases causing wheel nut loosening
Solution Approach 1:
The braking control is segmented into two phases: the first phase uses continuous switching element activation to deliver strong braking power when the motor is running at high speed, while the second phase uses PWM control to reduce reaction force when the motor slows down. This segmentation allows optimal braking power delivery without excessive reaction force.
Solution Approach 2:
The control method dynamically transitions from continuous switching element activation to PWM control based on the motor's rotation speed. This dynamic adjustment ensures that the control strategy adapts to the changing operational conditions, providing strong braking when needed and minimizing reaction force when the motor slows down.
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
This approach effectively inhibits reaction and voltage jumping, allowing for a balanced solution that reduces the risk of wheel nut loosening and voltage overload, enabling the use of smaller capacitors with lower withstand voltage.
Implementation Method 1
an inverter circuit supplying an electric current to the motor
Implementation Method 2
a capacitor provided on an input side of the inverter circuit
Data Source
AI summary
An electric tool capable of achieving inhibition of reaction due to braking in good balance with inhibition of voltage jumping due to regenerated energy is provided. A grinder (1) is provided with a motor (6), an inverter circuit (43) for supplying electric current to the motor (6), and a controller (50) for controlling the inverter circuit (43). When generating an electric braking force on a motor (6), the rotation speed of which exceeds a specified rotation speed, the controller (50) performs a first braking control of continuously turning on lower arm-side switching elements (Q4-Q6) of the inverter circuit (43), after which the controller performs a second braking control of repeatedly turning on and off the lower arm-side switching elements (Q4-Q6).