Duty Ratio Control for Rapid Motor Reacceleration
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Solution Overview
Problem
In electric power tools, when a motor is reaccelerated during deceleration after a stopping manipulation, the rotation speed cannot be rapidly increased if the voltage is controlled at the same duty ratio as during initial acceleration, as the motor is already rotating and has rotational energy, leading to inefficient speed recovery.
Innovation Solution
A duty ratio control device and electric power tool configuration that includes a duty ratio calculation unit and a parameter setting unit, where the duty ratio for reacceleration is set higher than for initial acceleration, based on parameters such as rotation speed, motor current, angle acceleration, and remaining battery power, to quickly increase motor speed during reacceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the same duty ratio control is used for both initial acceleration and reacceleration, then the control logic is simple, but the rotation speed cannot be rapidly increased during reacceleration
Solution Approach 1:
The patent applies dynamics by making the duty ratio control adaptive to different operational states. The control device dynamically adjusts the duty ratio based on whether the motor is in initial acceleration (from stopped state) or reacceleration (during deceleration period), allowing optimal speed increase for each state without requiring overly complex predetermined schedules.
Solution Approach 2:
The patent changes the duty ratio parameter based on the motor's operational state. During reacceleration, the duty ratio is set higher than during initial acceleration, enabling rapid speed recovery. This parameter adjustment resolves the contradiction by optimizing speed increase while maintaining manageable control logic through state-based differentiation.
2Speed
If a high duty ratio is applied during reacceleration to rapidly increase speed, then the rotation speed increases quickly, but the reaction on the electric power tool increases
Solution Approach 1:
The control device dynamically adjusts the duty ratio based on the motor's current rotational state. By detecting that the motor is in a deceleration state and transitioning to reacceleration, the system applies higher duty ratio only when necessary, achieving rapid speed recovery while minimizing unnecessary reaction forces that would occur with continuously high duty ratios.
Solution Approach 2:
The control device performs preliminary detection of the motor's operational state (stopped vs. rotating during deceleration) before applying the duty ratio. This preliminary action allows the system to prepare appropriate control parameters that balance speed recovery needs with reaction force minimization, rather than applying fixed high duty ratios that would increase reaction unnecessarily.
3Speed
If the duty ratio is set high for rapid acceleration, then the rotation speed reaches target quickly, but overshooting the target rotation speed occurs when target speed is low
Solution Approach 1:
The patent applies local quality by differentiating control strategies based on the specific operational context. Initial acceleration from stopped state uses one duty ratio approach, while reacceleration during deceleration uses a different approach. This localized control quality ensures rapid speed recovery during reacceleration without causing overshooting, as each operational phase receives tailored control parameters.
Solution Approach 2:
The control system dynamically adapts the duty ratio based on the motor's current state and target speed relationship. During reacceleration, the system applies higher duty ratios appropriately without causing overshooting by considering the motor's existing rotational momentum and the specific reacceleration context, thereby achieving both rapid speed recovery and precise control.
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 higher duty ratio for reacceleration allows for rapid increase in motor rotation speed while minimizing reaction on the electric power tool, even when starting from a faster rotation speed or higher load conditions, thus improving the tool's usability and efficiency.
Implementation Method 1
a motor (22) that receives electric power to rotate
Data Source
Figure 1
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AI summary
A duty ratio control device (100) includes a duty ratio calculation unit (102) and a parameter setting unit (102). The duty ratio calculation unit (102), when an acceleration manipulation is performed, calculates a control duty ratio per predetermined timing based on a value of at least one parameter so that a rotation speed of a motor (22) mounted on an electric power tool (10) reaches a target rotation speed corresponding to the acceleration manipulation. The control duty ratio is calculated to be larger as the value of the at least one parameter is larger. The parameter setting unit (102) sets the value of the at least one parameter. The value of the at least one parameter set for a reacceleration manipulation is larger than the value of the at least one parameter set for an initial acceleration manipulation.