Bidirectional Motor Control for Surgical Instruments
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Solution Overview
Problem
Current bidirectional control methods for electric motors in surgical and dental instruments cause significant mechanical shocks due to rapid direction reversals, leading to practitioner fatigue and decreased precision.
Innovation Solution
A method for bidirectional motor control that applies a control signal with a lower slope during the central part of the cycle, allowing for reduced acceleration and deceleration times, and maintaining constant speed between direction reversals, resulting in a trapezoidal or square-shaped control signal profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the motor is continuously accelerated from standstill to maximum speed with a triangular control setpoint, then the cutting blade can complete the required number of turns in each direction, but the motor is subjected to violent mechanical shocks due to inertia during rapid deceleration and direction reversal
Solution Approach 1:
The patent applies a dynamic control signal profile that adapts the acceleration and deceleration rates throughout the oscillation cycle. The slope of the control signal is continuously adjusted to be lower during central parts of the cycle and higher during initial and final parts, creating a non-uniform speed profile that reduces inertial shocks while maintaining cutting performance
Solution Approach 2:
The patent changes the temporal parameters of the control signal by varying the slope (dV/dt) at different phases of the oscillation cycle. This parameter modification allows the motor to reach necessary speeds for cutting while controlling the rate of change to minimize mechanical shocks during direction reversals
2Object-generated harmful factors
If more time is reserved for motor deceleration to reduce the violence of jerks, then the mechanical shocks are slightly reduced, but the time available for motor acceleration decreases, requiring even faster acceleration to meet blade operating requirements
Solution Approach 1:
The patent implements a dynamic balance between acceleration and deceleration phases by adjusting the control signal slope throughout the cycle. The system optimizes the timing and magnitude of acceleration/deceleration events to reduce shocks without compromising the total time available for blade operation in each direction
3Productivity
If the motor reaches high speed of 45,000 revolutions/minute to complete six turns in each direction, then the cutting blade can perform adequately, but only about 40 ms remains for deceleration and stopping before direction reversal
Solution Approach 1:
The patent begins deceleration earlier in the cycle and maintains a lower control signal slope during central phases, preparing the motor for direction reversal in advance. This preliminary action allows the motor to maintain high speeds for cutting while having sufficient time to decelerate smoothly before reversal
Solution Approach 2:
The system dynamically adjusts the motor speed profile to maintain high velocities during the central cutting phases while implementing controlled deceleration during transition phases, optimizing both productivity and mechanical comfort
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 significantly reduces the shocks felt during motor direction reversals, making the instrument more comfortable to hold and use, while maintaining tissue cutting efficiency and precision.
Implementation Method 1
an electric motor which drives alternately in one direction and in the opposite direction a cutting blade
Implementation Method 2
the motor is subjected to violent mechanical shocks due to the inertia of its rotor
Data Source
Figure 1A~1B
Figure 2A~3
Figure 4~5
AI summary
The invention relates to a method for the bidirectional control of an electric motor alternatively driving the cutting blade of a surgical or dental instrument in one direction or in the opposite direction, characterised in that it comprises, during a cycle (C) between two successive reversals of the cutting blade driving direction, applying to the motor a control signal having a profile the slope of which, in terms of absolute value, is essentially lower during a central part (t4) of the cycle (C) than the slope, also in terms of absolute value, of an initial part (t3) of said cycle (C) during which the motor is accelerated and of a final part (t5) of the cycle (C) during which the motor is slowed down.