Articulated Crane Arm Height Control via Multi-Sensor Feedback
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Solution Overview
Problem
Articulated cranes and elevating work platforms face inaccuracies in controlling height variations of the end-effector due to load variations, as existing compensation techniques fail to account for mounting allowances and deformations in the articulated arm, leading to safety hazards such as collision or inability for personnel to reboard the basket.
Innovation Solution
The implementation of a system with multiple sensors to measure the theoretical and actual height of the end-effector, using a control unit to adjust the position of the end-effector by actuators, considering deformations and load variations, ensuring accurate height control both statically and dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauges are used to measure structural deformations of the arms, then it is possible to compensate the variations of height of the end-effector caused by deformations, but the compensation technique is inaccurate because it does not allow for other factors such as mounting allowances of the extensions
Solution Approach 1:
The measurement system is segmented into multiple independent sensors positioned at different locations along the articulated arm. Each sensor measures local deformation or position, and the control unit processes these segmented measurements to calculate the total height variation, accounting for both structural deformations and mounting allowances of extensions.
Solution Approach 2:
The control unit acts as an intermediary that receives data from multiple sensors and processes it to determine the actual height of the end-effector. It calculates height variations by considering both the deformations measured by strain gauges and the mounting allowances of extensions, providing a more accurate compensation than direct strain gauge measurement alone.
2Reliability
If the basket is positioned at a right height for enabling persons to easily descend, then the persons can descend safely, but as soon as the basket is empty, it moves up to a higher level and persons will not be capable to get up again
Solution Approach 1:
The control unit continuously receives feedback from multiple sensors about the actual height of the end-effector (basket) and compares it with the desired height. When the basket becomes empty or when height variations are detected, the system automatically adjusts the basket position to maintain the correct height for safe boarding and disembarking, preventing the basket from moving to an unsafe higher level.
Solution Approach 2:
The system performs preliminary height compensation before the basket is fully loaded or unloaded. By continuously monitoring height variations and pre-adjusting the basket position, the system ensures that the basket remains at the correct height for safe operation throughout the loading and unloading process, preventing unsafe conditions before they occur.
3Productivity
If the crane unloads the materials, then the materials can be delivered to the recess, but the elastic deformation of the arm disappears and the crane can hit the structure where the recess is located
Solution Approach 1:
The system performs preliminary height compensation before the crane arm returns to its initial position after unloading. By detecting the load removal and predicting the elastic deformation recovery, the control unit pre-adjusts the arm position to account for the upward movement that will occur when deformation disappears, preventing collision with the recess structure.
Solution Approach 2:
The control unit applies a preliminary counteracting adjustment to compensate for the elastic deformation recovery. When the load is removed, the system detects the change and applies an opposing adjustment to the arm position to counteract the upward movement caused by deformation disappearance, preventing the crane from hitting the structure.
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 enables precise control of the end-effector's height, preventing collisions and ensuring safe operation by accurately compensating for deformations and load-induced variations, maintaining stability and usability of the crane or EWP.
Implementation Method 1
Due to the load applied at the end-effector, the articulated arm is subjected to elastic deformations which disappear when the load is removed.
Data Source
Figure 1~2
AI summary
An articulated arm (101) comprises: - a plurality of bodies consecutively connected in order to form an open kinematic chain with an end-effector (105), having a plurality of translative and/or rotative degrees of freedom and a plurality of actuators for moving said bodies; - one or more first sensors associated to said bodies, adapted to supply signals indicative of linear or angular positions of the bodies of the kinematic chain in order to enable to determine a theoretical height of the end-effector (105); - at least one second absolute angular sensor adapted to measure an absolute angle of the body of the kinematic chain where the end-effector (105) is located, and to provide a signal indicative of the same; - a control unit operatively connected to said actuators, to said one or more first sensors, and to said at least one second absolute angular sensor, configured to: - determine said theoretical height of the end-effector (105) based on the signals from the one or more first sensors; - estimate a height variation of the end-effector (105) between the theoretical height and an effective height determined by loads applied to the arm based on signals from the one or more first sensors and from the at least one second absolute angular sensor; - commanding the actuators to reduce the estimated height variation of the end-effector (105).