Cam-Based Closed-Loop Speed Control for Power Tool Reload Cycles
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Solution Overview
Problem
Existing power tools lack efficient closed loop speed control mechanisms to manage motor speed during reload cycles, leading to potential energy wastage and overshot issues.
Innovation Solution
Implementing a closed loop speed control system using a sensor to detect a predetermined rotational position of a cam, comparing a motor parameter to a threshold value, and initiating a speed ramp down when the parameter exceeds the threshold, thereby controlling motor speed during reload cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If motor speed is increased to improve productivity during reload cycles, then the reload speed increases, but energy consumption increases and overshot issues occur
Solution Approach 1:
The patent implements closed-loop speed control by monitoring motor speed via a sensor and dynamically adjusting power delivery based on real-time speed feedback. The controller compares actual speed against a target speed and modulates power accordingly, enabling the system to achieve high productivity while consuming less energy through precise control rather than brute-force high-speed operation throughout the entire cycle.
Solution Approach 2:
The system dynamically adjusts motor speed and power delivery during the reload cycle based on actual operational conditions. Rather than maintaining constant high speed, the controller modulates speed in real-time, increasing it when needed for productivity and reducing it when approaching completion or under varying load conditions, thereby optimizing the balance between productivity and energy consumption.
2Productivity
If motor speed is increased to complete reload cycles faster, then productivity improves, but overshot issues occur leading to reduced manufacturing precision
Solution Approach 1:
The closed-loop control system continuously monitors motor speed and position via sensors and provides real-time feedback to the controller. This enables precise control of the driver blade's motion during reload cycles, allowing the system to complete cycles quickly while maintaining manufacturing precision by making real-time adjustments to prevent overshot conditions.
Solution Approach 2:
The controller anticipates potential overshot conditions by monitoring motor parameters and proactively adjusting power delivery before the driver blade reaches its target position. This preliminary action prevents overshot from occurring in the first place, enabling fast reload cycles without compromising the precision of driver blade positioning.
3Device complexity
If simple speed control is used to reduce device complexity, then the system becomes simpler, but energy wastage and overshot issues cannot be effectively managed
Solution Approach 1:
The patent incorporates feedback-based speed control where a sensor monitors motor speed and feeds this information back to the controller, which then adjusts power delivery accordingly. This relatively simple feedback mechanism effectively manages energy consumption by avoiding unnecessary high-speed operation and preventing overshot conditions, thereby reducing energy wastage without requiring complex control systems.
4Productivity
If high motor speed is maintained throughout the reload cycle to improve productivity, then reload time decreases, but energy consumption increases unnecessarily during deceleration phases
Solution Approach 1:
The control system applies periodic modulation to motor speed during the reload cycle, varying speed according to the specific phase of operation. During acceleration and mid-cycle phases, higher speeds are applied to reduce overall reload time, while during deceleration and positioning phases, speed is reduced appropriately. This periodic action optimizes the balance between productivity and energy efficiency by matching speed to operational needs throughout the cycle.
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 closed loop speed control system effectively manages motor speed, reducing energy consumption and preventing overshot, especially when battery impedance is low, enhancing operational efficiency.
Implementation Method 1
The sensor is a Hall effect sensor that is configured to detect a position of the magnet
Data Source
AI summary
A power tool including a housing, a motor at least partially positioned within the housing, a driver blade extending along a driving axis, and a cam assembly including a cam that is configured to rotate about a rotational axis to move the driver blade. The cam includes a target that rotates with the cam. A sensor is configured to detect the target when the target is at a predetermined rotational position of the cam. A controller is connected to the motor and the sensor. The controller is configured to receive a signal from the sensor indicating that the target is at the predetermined rotational position of the cam, compare a motor parameter to a threshold value, and initiate a speed ramp down in response to the target being at the predetermined rotational position of the cam and the motor parameter being greater than or equal to the threshold value.