Slew Drive Control for Paving Machine Seizure Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Paving machines equipped with slew drives often experience component failures due to over or under-driving, leading to lock-ups and axial overload issues, particularly with tapered roller bearings, which can result in reduced operational efficiency and increased maintenance costs.
Innovation Solution
A paving machine system that includes a processor-controlled slew drive system with angle sensors and pressure transducers to detect seizures and adjust power supply, engaging the slew drive in reverse rotational directions to prevent lock-ups and manage hydraulic pressure, thereby reducing component stress and failure rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a slew drive is used to provide rotational movement with a greater range of motion, then the range of motion is improved, but the reliability deteriorates due to component failures from over or under-driving and lock-ups
Solution Approach 1:
The control system continuously monitors the actual angular position of the slew drive output via angle sensors and compares it against commanded positions. When discrepancies indicate over-driving or under-driving conditions, the system automatically adjusts or reverses drive direction, preventing component failure while maintaining the full range of motion capability.
Solution Approach 2:
The system employs reverse rotational capability as a protective mechanism. When the slew drive approaches operational limits or exhibits signs of over-driving, the control system engages reverse rotation to back out the excessive movement, thereby preventing lock-ups and component failure while preserving the forward range of motion.
2Power
If the slew drive operates at high torque to meet paving machine requirements, then the power output is improved, but the reliability deteriorates due to axial overload on tapered roller bearings
Solution Approach 1:
Pressure transducers monitor hydraulic pressure within the slew drive system in real-time. When pressure exceeds thresholds indicating axial overload on the tapered roller bearings, the control system reduces or terminates the torque application, preventing bearing failure while maintaining the capability to deliver high torque when needed.
Solution Approach 2:
The control system preemptively monitors operating conditions and anticipates overload scenarios. By detecting trends in pressure and angular position data, the system takes preventive action before actual bearing overload occurs, cushioning against failure while preserving full power output capability.
3Power
If the slew drive uses internal gearing to increase torque multiplication, then the output torque is improved, but the device complexity increases leading to over or under driving and lock-ups
Solution Approach 1:
The control system monitors the actual angular displacement of the slew drive output shaft and compares it against the commanded displacement. When the internal gearing causes over-driving (excessive rotation) or under-driving (insufficient rotation), the feedback mechanism detects the discrepancy and adjusts the commanded input angle, compensating for the complex gear ratios and preventing lock-ups.
Solution Approach 2:
The system replaces manual mechanical adjustment of gear ratios with an electronic control system that calculates and compensates for the fixed gear ratios. The processor automatically determines the correct input angles based on sensor feedback, eliminating the need for mechanical complexity in the control mechanism while maintaining the torque multiplication benefits of the internal gearing.
Data Source
AI summary
A slew drive includes a bushing interfacing with a drive gear. The bushing resists a load from the drive gear. The bushing includes an aluminum bronze alloy with a high strength. A paving machine includes multiple of the slew drives. The slew drives control an angle of a pivot arm and steering of a track. A method of reducing component failure in the paving machine includes determining an angular position error of the slew drive of the track. If the angular position exceeds a tolerance, a rate-of-change of the angular position is found to determine whether the slew drive is rotating. Where the slew drive is not rotating, the slew drive is driven in a reverse direction to unseize the slew drive. A track drive and the slew drive of the pivot are controlled by a control loop. The slew drive may be dithered to steer a trailing pivot.