The design of a three point linkage implement height control system

Clarke, Daniel John (2006) The design of a three point linkage implement height control system. [USQ Project]


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The purpose of this project was to design a height control system that could be applied to
a Three Point Linkage mounted implement. Several methods of achieving this goal were
investigated. The two methods that were investigated in detail were an electrical over
hydraulic system and a mechanical over hydraulic system.
The unique operation of the three point linkage implements when lift assist is used
presents problems when accurate frame height is required, such as when seeding
operations are being performed. The system has been designed so that it is constantly
sensing the height of the frame at both ends of the implement. The output from this
sensing is used to control a hydraulic valve mechanically or electrically. If a height
discrepancy between the front and rear of the implement is detected, this valve will be
activated to allow a flow of hydraulic oil to the lift assist system, levelling the implement.
The investigation of the electrical control system involved constructing a prototype
circuit that was based on a PICAXE microcontroller to provide computing power. This
chip was programmed to read the output from two variable resistors and detect any height
discrepancies. When a discrepancy was detected, the microcontroller activated a
servomechanism that used mechanical motion to correct the position of one of the resistor
to match the mechanical position of the two resistors, thus proving the concept of
mechanical height control.
The mechanical system was designed so that the output from two height sensing wheels
was mechanically input into the hydraulic valve to actuate it when the wheels sensed that
there was a height discrepancy. This system was modelled using the solid modelling
package SolidWorks and basic engineering analysis was performed on the design.

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Item Type: USQ Project
Refereed: No
Item Status: Live Archive
Faculty/School / Institute/Centre: Historic - Faculty of Engineering and Surveying - Department of Mechanical and Mechatronic Engineering (Up to 30 Jun 2013)
Date Deposited: 11 Oct 2007 01:05
Last Modified: 02 Jul 2013 22:44
Uncontrolled Keywords: PICAXE; SolidWorks; height control system
Fields of Research (2008): 09 Engineering > 0913 Mechanical Engineering > 091399 Mechanical Engineering not elsewhere classified
09 Engineering > 0913 Mechanical Engineering > 091302 Automation and Control Engineering
Fields of Research (2020): 40 ENGINEERING > 4017 Mechanical engineering > 401799 Mechanical engineering not elsewhere classified
40 ENGINEERING > 4007 Control engineering, mechatronics and robotics > 400799 Control engineering, mechatronics and robotics not elsewhere classified

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