Bi-directional Cable Drive Actuator for Low Hysteresis
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Solution Overview
Problem
Existing compact actuator systems for vehicles face challenges such as space constraints, reliability, hysteresis, and the need for quick response, particularly in applications like vehicle door damping and control, where high forces must be absorbed in a short distance with minimal play and energy absorption during door movement.
Innovation Solution
A bi-directional element drive system utilizing an inexpensive electric motor with a cable-based mechanism, where a drive shaft, cable anchor, and cable connector work together to displace a driven element between positions, often with a pulley system and optional spring to minimize play, allowing for compact and reliable operation without traditional transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a traditional gear-driven system is used to achieve compact actuation, then space constraints are addressed, but hysteresis and play are introduced into the system
Solution Approach 1:
The patent replaces the traditional gear-driven mechanical transmission system with a direct-drive mechanism where the motor shaft is directly connected to the cable drum. This eliminates the gear train that causes hysteresis and play, while maintaining compact actuation through the integrated motor-cable drum design
Solution Approach 2:
The patent removes the traditional transmission components (gears, belts, chains) from the actuator system, extracting only the essential motor and cable-driven mechanism. This eliminates the sources of hysteresis while preserving the compact form factor through direct coupling of motor to load
2Force
If a large motor is used to deliver high force, then force capability is improved, but motor size and system weight increase
Solution Approach 1:
The patent introduces a cable system as an intermediary mechanism between the motor and the driven element. The cable acts as a flexible transmission medium that allows a small motor to generate high force through mechanical advantage, similar to a pulley system, while maintaining compact size and reducing weight
Solution Approach 2:
The patent transitions from direct linear or rotary force application to a cable-based system that operates in a different dimensional space. The cable wraps around a drum, converting rotational motor motion into linear cable tension, effectively multiplying force while keeping the motor small
3Measurement precision
If play is eliminated in the drive system to improve precision, then control accuracy is improved, but system complexity and cost increase
Solution Approach 1:
The patent replaces complex mechanical pre-loading mechanisms, anti-backlash gears, or precision ball screws with a simple cable-driven direct-drive system. The cable-natural tension characteristic inherently eliminates play without requiring additional complexity, achieving precision through simplicity
Solution Approach 2:
The cable system inherently maintains tension and eliminates play through its own physical properties. The cable remains taut during operation, providing self-centering and eliminating the need for external pre-loading mechanisms or complex control systems to compensate for backlash
4Speed
If the actuator is designed for quick response with high force absorption, then response time is improved, but energy management complexity increases
Solution Approach 1:
The patent incorporates a spring element in the cable system that stores energy during door closing (absorbing the impact energy) and releases it during door opening. This recovers energy that would otherwise be lost, reducing the energy management complexity while enabling quick response and high force absorption
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 system achieves low hysteresis, high force capability with small motor size, and the ability to function manually in power failures, offering a cost-effective, space-efficient solution with reduced weight and complexity, suitable for various applications like doors, gates, and aircraft control surfaces.
Implementation Method 1
a cable-based mechanism, where a drive shaft, cable anchor, and cable connector work together to displace a driven element between positions
Implementation Method 2
the cable connector also includes a spring to eliminate play
Data Source
AI summary
A bi-directional element drive system includes a motor having a drive shaft, a cable anchor and a cable connector. The cable connector is carried on the drive shaft and has two ends connected to the cable anchor. In addition the drive system includes a support and a driven element. The driven element is displaced between a first position and a second position relative to the support by the motor.