Study on Various Position Sensing Technologies in T ractor Hitch Application

Conventionally, In the tractors, hitch position is obtained using a contact-based position sensor, the sensor is attached to the rockshaft mechanically with gears or linkages. In this arrangement, there are incidences of failures when working with heavy implements, as rockshaft is under severe loading conditions which tends to induce cracks or failures in sensor mechanical linkages mounting area. This results in machine downtime and rockshaft repair costs to the customer. These mounting threads in hardened Rockshaft reduce material strength which impacts the lifting capacity. There is associated difficulty at assembly line and further during maintenance for linkage installation and adjustments. Also, over the period, linkages develop a play at joints due to the friction.

In the present work, we are sensing the Hitch position with contactless sensor technology. A contactless Hall effect sensor is selected, and proto setup has been designed to measure the hitch position by integrating the sensor and target. The prototype consists of a fixed Sensor and a rotating metal (ferromagnetic) piece placed inside a 3D printed casing. The profile of metal piece is such that when it is rotated about the axis, the distance between Sensor and metal piece changes gradually. This causes different output voltage at different amount of rotation in metal piece. Results from manual bench testing show that the concept is working. The sensor voltage output varies according to the hitch position in the bench setup. A high voltage value when metal piece is nearer to magnet and low value when its farther. A future step is to automate this setup on a tractor to remove errors due to manual rotation. This would be an enabler to analyze the sensor behaviors like hysteresis, repeatability, linearity more accurately.