Pedal Vehicle Powertrain Angular Position Control

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Solution Overview

Problem

The existing powertrain for pedal vehicles, such as bicycles, experiences limited dynamic response capability due to measurement time lags in speed measuring systems, leading to a slipping sensation and impaired torque transfer from the pedal to the output chainring, which affects the user's experience and the overall performance of the system.

Innovation Solution

The powertrain employs a configuration where the second motor engages with the crank axle and the first motor is connected to the sun gear, with the planet carrier attached to the output chainring and the ring gear connected to the pedal, using sensors to measure angular positions and currents to regulate both motors in closed loops, allowing for proportional assistance without additional torque sensors and enhancing control dynamics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If speed measurement is performed using position sensors with time-based calculation, then the system can measure angular velocity, but measurement time lag is introduced which limits dynamic response

Engineering Contradiction:

Improveangular velocity measurementVSAvoidmeasurement time lag

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces the mechanical/time-based speed measurement system with a direct angular position feedback system. Instead of calculating speed from position changes over time, the control unit directly regulates the first motor based on angular position feedback, eliminating the time lag inherent in differentiation-based speed measurement.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Speed

If the first motor is regulated based on speed feedback with time lag, then speed control is achieved, but dynamic response is limited causing slipping sensation

Engineering Contradiction:

Improvemotor speed controlVSAvoidtorque transfer reliability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent inverts the control approach by regulating the first motor based on angular position rather than derived speed feedback. This inversion eliminates the time lag and improves dynamic response, ensuring reliable torque transfer from pedal to output chainring without slipping sensation.

Inventive Principle:

Principle #13The other way round (Inversion)

3Reliability

If high resolution position sensors are used for both motors, then control dynamics are improved, but device complexity increases

Engineering Contradiction:

Improvecontrol dynamicsVSAvoidsensor system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent uses the angular position sensor on the second motor to serve dual purposes: measuring the second motor's position for torque control and providing feedback for regulating the first motor's angular position. This multi-functionality improves control dynamics without requiring an additional high-resolution position sensor on the first motor.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS10479447B2Powertrain for a pedal vehicle

Publication Date: 2019.11.19 E2 DRIVES SA

AI summary

Powertrain for a pedal vehicle Powertrain for a pedal vehicle comprising a first (20) and a second (4) motor as well as an planetary gearing (3) having a planet carrier (14, 114), a ring gear (12, 112) and a sun gear (13), which first motor (20) is connected to the planetary gearing (3), which powertrain also comprises a crank axle (11) to which the ring gear (12, 112) is connected to create a first input to the planetary gearing (3), the second motor (4) is geared to the crank axle (11), a control unit (6) being designed to regulate the first motor (20) according to an angular position setpoint, and the second motor (4) according to a current or torque setpoint.