Lifting Cart Positioning with Encoder and Laser Sensors
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Solution Overview
Problem
Automated storage and retrieval systems (AS/RS) face inaccuracies in positioning automated lifting storage carts due to wheel deformation under load, leading to potential collisions and inefficiencies, especially with urethane wheels, which deform significantly, and steel wheels, which can slip, causing errors in distance calculation using encoder-based systems.
Innovation Solution
The system incorporates a cart with multiple drive sets, a calibration surface, and sensors to accurately determine the cart's position by compensating for wheel deformation and using additional positioning methods like laser rangefinding or photo sensors to ensure precise location, reducing errors and improving safety and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If urethane wheels are used to improve grip, then friction and grip are improved, but wheel deformation under load increases causing encoder positioning errors
Solution Approach 1:
A fifth wheel encoder wheel is introduced as an intermediary component that contacts the railway directly to provide accurate position feedback, independent of the drive wheel deformation. This mediator transfers positional information without being affected by load-induced deformation of the urethane drive wheels.
Solution Approach 2:
The patent replaces reliance on encoder feedback from deformable drive wheels with an optical measurement system (laser emitter and detector) that measures actual position optically, substituting a mechanical measurement method prone to deformation errors with a non-contact optical method.
2Measurement precision
If steel wheels are used to reduce deformation, then positioning accuracy is improved, but slippage on rails increases causing encoder errors
Solution Approach 1:
The fifth encoder wheel acts as an intermediary that provides accurate rotational position feedback independent of drive wheel slippage. It contacts the rail directly at the encoder location to measure actual position without being affected by slippage of the drive wheels.
Solution Approach 2:
The system uses feedback from the fifth encoder wheel and optical measurement to detect and correct positioning errors caused by slippage, continuously adjusting to maintain accurate position information despite slippage events.
3Device complexity
If encoder counts are used to determine distance traveled, then positioning is simplified, but wheel deformation introduces cumulative errors
Solution Approach 1:
The fifth encoder wheel serves as an intermediary measurement device that directly contacts the railway to provide accurate position feedback independent of drive wheel deformation, correcting cumulative encoder errors without significantly increasing system complexity.
Solution Approach 2:
The patent introduces optical measurement (laser emitter and detector) as a non-mechanical method to measure actual distance traveled, replacing reliance on mechanical encoder counts that accumulate errors from wheel deformation.
4Measurement precision
If laser rangefinding is used to accurately determine position, then positioning accuracy is improved, but device complexity increases
Solution Approach 1:
The laser emitter and detector are integrated into the existing cart structure to perform multiple functions: measuring distance for positioning accuracy while also potentially serving as a reference for encoder calibration and collision detection, reducing the impact of added complexity.
Solution Approach 2:
The optical measurement system acts as an intermediary that provides accurate position feedback to the control system, enabling precise positioning while the control system integrates this information with encoder data to manage overall system complexity.
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 solution enhances the accuracy of cart positioning, reduces the risk of collisions, and improves operational efficiency by compensating for wheel deformation and using multiple sensors for precise distance calculation, thereby ensuring accurate and reliable storage and retrieval operations.
Implementation Method 1
an encoder reading a property of rotation of a rotating element of the cart
Implementation Method 2
a motor to drive at least one of the wheels to propel the cart in the railway
Data Source
AI summary
A system for positioning a lifting cart in an automated storage facility is described. In one example, the system includes a motorized lifting cart configured to move about a railway of a storage area. An encoder on the cart reads a property of rotation of a rotating element on the cart, and a controller may receive the property of rotation from the encoder and convert it to a rotation count of the rotating element. The rotating element may be an encoder shaft, drive shaft, and like elements. Some systems include a signal emitter or photo sensor to position the lifting cart and to facilitate providing instructions to the cart.