Power Tool Motor Torque Alerts for Haptic User Notification
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Solution Overview
Problem
Existing power tools, such as electric chain saws, struggle to effectively notify users of certain conditions without diverting their attention from the task at hand, especially when wearing ear protection and gloves, making visual or auditory alerts ineffective.
Innovation Solution
Implementing a control unit that varies motor torque using field-oriented control (FOC) to produce haptic feedback or characteristic sound patterns, allowing users to feel or hear notifications through the tool's motion and sound, without altering the rotational speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If visual or auditory alerts are used to notify users of tool conditions, then user awareness of conditions is improved, but user attention is diverted from the work process
Solution Approach 1:
The notification function is segmented from traditional visual/auditory channels and integrated into the motor control system itself. The motor torque variations serve as the notification medium, separating the notification function from separate indicators while utilizing the existing motor actuation path.
Solution Approach 2:
The motor system serves dual purposes: it performs the primary function of driving the tool while simultaneously providing the notification function through torque variations. The motor acts as both the work-producing element and the communication element, eliminating the need for separate notification devices.
2Loss of information
If separate notification devices such as piezo-electric buzzers or indicator lamps are used, then user notification is improved, but device complexity increases
Solution Approach 1:
The notification function is merged with the motor control system. The same control unit that manages motor operation also generates notification signals by modulating motor torque, combining two functions into a single integrated system.
Solution Approach 2:
The motor is given multiple functions: it drives the tool operation and simultaneously serves as a notification device through controlled torque variations. This multi-functionality eliminates the need for dedicated notification components.
3Loss of information
If auditory notifications are used, then user awareness is improved, but effectiveness is reduced when users wear ear protection
Solution Approach 1:
The motor torque variations act as an intermediary medium for communication. Instead of directly transmitting auditory signals that are blocked by ear protection, the system uses mechanical torque pulsations that propagate through the tool structure to the user's hand, bypassing the blocked auditory channel.
Solution Approach 2:
The auditory notification system is replaced with a mechanical haptic notification system. Torque pulsations create detectable vibrations and motions in the tool that the user can feel through their hand, substituting the blocked auditory sense with an intact tactile sense.
4Loss of information
If torque variations are used for notification, then user notification is achieved, but rotational speed control may be affected
Solution Approach 1:
Notification is achieved through periodic torque pulsations superimposed on the base torque. These periodic variations are designed with specific frequencies and duty cycles that create detectable haptic feedback while being distinguishable from the steady-state operation, allowing the control system to maintain average speed while providing notification signals.
Solution Approach 2:
The control system dynamically adjusts motor parameters, specifically varying torque while maintaining speed control. By using field-oriented control, the system can independently control torque and speed, allowing torque pulsations for notification without compromising rotational speed stability.
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
Enables safe and reliable communication of tool conditions, such as low chain oil or battery level, without requiring visual or auditory distraction, enhancing user awareness and safety.
Implementation Method 1
a control unit configured to detect a condition to be communicated to a user of the power tool, and to vary, for instance using field-oriented control, FOC, the motor torque according to a predetermined pattern as a notification in response to the condition
Data Source
AI summary
The present disclosure relates to an electric power tool (1) comprising at least one handle (31, 33) and an active tool part (2, 4) powered by and electric motor (5), wherein the electric motor is powered by a supply unit (13, 23) controlling the electric motor torque. A control unit (41) detects a condition to be communicated to a user of the power tool, and to vary, for instance using field-oriented control, FOC, the motor torque according to a predetermined pattern as a notification in response to the condition, such that a motion of the tool (1) is produced or a characteristic sound pattern. Such a notification can be relatively easily noticed by a user under working conditions.