PWM-Controlled Motor-Generator for Variable Exercise Load
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Solution Overview
Problem
Existing exercise machines are limited in their ability to efficiently dissipate energy and control load variations quickly, leading to inefficient power dissipation and limited mechanical load simulation capabilities.
Innovation Solution
An exercise machine with a PWM-controlled electrical circuit, featuring a switching element, PWM controller, load reference controller, and electrical resistor, allowing for fast and precise load control at specific locations of the user force input element, decoupling the load resistance from the motor for optimized placement and cooling, and using a DC motor for efficient energy use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mechanical loads (large mass or friction devices) are used to provide resistance, then the exercise machine can simulate varying loads, but the system becomes complex and requires large mechanical components
Solution Approach 1:
The patent replaces the mechanical load simulation system (large masses, friction devices) with an electrical system consisting of a DC motor operating as a generator connected to electrical resistors. The motor generates electrical current when turned by the user, and this current is dissipated through resistors controlled by PWM circuitry, thereby simulating mechanical load variations without requiring complex mechanical components.
2Ease of operation
If electrical devices (motor as generator with resistive load) are used to provide load, then the system can control load variations, but the power dissipation capability is limited
Solution Approach 1:
The patent divides the electrical load into multiple separate resistor elements (first resistor, second resistor, etc.) that can be independently controlled through PWM circuitry. This segmentation allows the system to manage power dissipation across multiple components, increasing the total power handling capability while maintaining precise control over the load applied to the user.
Solution Approach 2:
The patent uses PWM (Pulse Width Modulation) control to dynamically change the effective resistance presented to the motor-generator. By varying the duty cycle of the PWM signal, the system can smoothly adjust the amount of power dissipated, enabling both fine load control and high power dissipation capability without changing physical resistor values.
3Measurement precision
If PWM control with high switching frequency is used, then the load can be controlled precisely at specific locations of the trajectory, but the device complexity increases
Solution Approach 1:
The patent introduces PWM controllers as intermediary devices between the user's mechanical input and the electrical load. The PWM controller receives control signals and translates them into precise switching commands for the power MOSFETs, thereby enabling fine-grained load control at specific positions in the pedal trajectory without requiring direct complex control of the power stage components.
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 efficient energy dissipation, precise load control, and flexible simulation of mechanical loads, extending the motor's lifespan and reducing the need for large mechanical components, while providing a smoother workout experience.
Implementation Method 1
the motor runs as a generator such that when the electric motor is turned, an electrical current is developed in the electrical circuit
Implementation Method 2
an electrical resistor... when the switching element is switched on and off, the electrical resistor is electrically connected and disconnected respectively from the electric motor
Data Source
AI summary
An exercise machine comprises a user force input element, a transmission unit, an electric motor, and an electrical circuit connected to the electric motor. The user force input element is connected to the electric motor via the transmission unit such that said electric motor turns at an angular velocity which is different than the velocity or angular velocity of the user force input element. The motor runs as a generator such that when the electric motor is turned, an electrical current is developed in the electrical circuit. The electrical circuit comprises an electrical resistor, a switching element, a Pulse Width Modulation (PWM) controller, and a load reference controller.