Development of an Embedded Weighing System for Semi-Trailers Based on Hall Effect Sensor 2023-36-0357

The measurement of the cargo weight on semi-trailer trucks is required to several stakeholders in the logistics market, for this information can reduce expenses on vehicle maintenance, risk for load traffic fines and ensures safer driving of the vehicle. The state-of-the-art on on-board weighing systems of semi-trailers with leaf spring suspension adopt several techniques to estimate the load: solutions based on load cells, vibrating-wires force transducers or strain gauges on the chassis, on the suspension springs or on the axles of the vehicle. In this work, a new system based on hall effect sensor was developed and tested for measurement of the axle load in semi-trailers through the linear movement that occurs between the trailer axle and its chassis. This solution has low sensitivity to environmental phenomena not caused by human intervention, such as humidity or temperature variations. A lab test was made to compare some arrangements of magnets and hall effect sensors to find out which interaction provides the best linear response for the displacement range. Next, a mechanical prototype and an embedded hardware were designed and assembled into a tank semi-trailer to test the system at the facilities of Librelato Semi-trailers factory. The test routine consisted of several known water loads in the tank of the semi-trailer, which would repeatedly position its axles over a certified weighbridge. A data acquisition software was developed to capture measure points during loading and unloading processes. When comparing to the weighbridge, the system response presented variations that goes from 15%, with an empty tank, to 2% error, with a fully load tank. The proposed system accomplished good results within the tests conditions and the traffic legislation and presents a competitive development cost, indicating that a further development could be done in order to reach the market.