A LOAD MEASUREMENT SYSTEM FOR COMMERCIAL VEHICLES
Field of invention
This invention is related to an on board load measurement system for commercial vehicles. The invention provides a digital display of Vehicle pay load, Pay load distribution and Pay load message alert to an operator.
Background ofinvention
Technology strides in the automotive sector enshrine its path alongside the features of providing better safety, performance and comfort to the customers. In the commercial vehicle segment, it is imperative to ensure that the vehicle is loaded only up to the manufacturer standards and not over-loaded.
Over-loading and uneven load distribution has contributed significantly to the upward accident trends and increase in vehicle downtime. This is augmented by the fact that the Directorate general of mining and safety - India (DGMS) has stipulated a clause for onboard payload systems in mining trucks. The above requirement has necessitated for the monitoring system that measures the payload of a vehicle.
Conventional load cell installation in the loading path was not feasible in this particular application since this may affect the critical factors like vehicle geometry, load distribution over the frame and safety. Hence there is a need of user friendly load measuring system with accuracy, serviceability and cost
effectiveness.

Objects of invention
The main objective of the present invention is to measure the payload of the vehicle by measuring axle bending indirectly and to display and transmit the data to the vehicle owner in remote location by utilizing appropriate electronic
devices.
Summary of the invention
In commercial vehicles, over loading and uneven loading is a regular practice. To ensure safe loading and tipping and to avoid fine for over loading, the present invention provides measurement of axle end (payload) loads as a
solution.
There are particular instances like tipping operation, non-uniform loading and uneven material density etc. which causes wheel end loads to shoot more than the safe limit of the axle. This needs to be brought to the vehicle operator's attention to ensure the safe loading.
The invention relates to a pay load sensor design and electronic circuit application for measuring and displaying the pay load of a commercial vehicle and to transmit to a receiver device like as mobile Phone or a PC. The proposed system is developed by the principle of load-cells mounted on the axle near the suspension to capture the axle bending during loading. The measured responses are calibrated for the loads and a display is placed on the vehicle dashboard for indication of payload and also the distribution of forces at each axle ends.

Though the payload sensors are available in the market, it isn't either financially viable or compatible with the packaging requirements of the vehicle. This has stirred for a design and development of low-cost custom payload measurement system. This axle mounted sensor is designed to measure the pay load indirectly and vehicle wiring harness has been modified to route the sensor output signals to the cabin mounted Electronic board. This electronic device is programmed to display the individual axle loads and pay load separately. This programmed board has got an additional feature of sending the pay load to the receiver on customer demand or preset intervals.
Brief description of drawings
Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same,
Figure 1 shows the layout of the sensor installation according to the present
invention, Figure 2a shows the isometric view of sensor design according to the present
invention, Figure 2b shows figurative representation to calculate the deflection to arrive at
the length of the sensor, Figure 3a & 3b shows the location of the sensor w.r.t rear and front axle
according to an embodiment of the present invention, Figure 4a shows the isometric view of sensing section with strain gauge
according to an embodiment of the present invention, Figure 4b shows the load acting on a cantilever beam based on which the strain
gauge according to the embodiment of the invention is developed, Fig. 4c shows the load acting on the axle with the corresponding bending
moment and deflection,

Figure 5 shows the orientation of the sensor according to an embodiment of the
present invention Figure 6 shows the calibration process according to the present invention Figure 7 shows the layout of the electronic device programmed to display the
individual axle loads and pay load
Detailed description of invention
The invention relates to a strain gauge based sensor (10} which works on indirect measurement of axle bending. The load acting on an axle (2a, 2b] of a vehicle (V) bends the axle (2a, 2b]. In the present invention sensors (10a, 10b) is mounted on both the front and rear axles (2a, 2b) and the sensors capture strain caused in the axle (2a, 2b) indirectly.
As the deflection of the axle depends on the distance between the wheels, hence the length of the sensor (10) is the most important parameter, since the deflection/sensitivity of the sensor increases as the length (10) of the sensor increases. To increase the sensitivity (as the measurement of lesser strain with cost effective measurement system is the biggest challenge) the moment of inertia of the sensing section is reduced as shown in Fig.2a.
The location of the sensor (10) w.r.t wheel (W) is very important consideration as the deflection between the wheel (W) and the spring seat area is a cubic function of the length from the wheel, while the deflection between the spring seat area and the differential (D) is the parabolic function of the length.
A representative illustration of the above is shown in Fig. 2b.
Deflection between the wheel and the spring seat

Deflection between the spring seat area and the differential

From the formula, it is clear that the length of the sensor ('x' in the formula) has direct impact on the deflection and hence response will increase with increase in length.
But because of the space constraint the sensor (10a, 10b] cannot be placed in between the wheel (W) and the suspension means, such as leaf springs (SF, SR). To utilize the effect of maximum deflection as well as space constraint in the rear axle (2b), the sensor (10b) is placed in such a way that the spring seat area (SUA) comes substantially at the center of the sensor (10b) and the sensing section (12b) is kept towards the differential side as shown in Fig.3a.
In the front axle (2a) the sensor (10a) is located between the suspension springs (SF) keeping the sensing section (12a) towards the center of the axle (2a) as shown in Fig.3b.
In another embodiment, the sensor section (12a, 12b) is a strain gauge and the orientation of the gauge is selected based on bending principle of straight beams. A cantilever beam was studied and the learning was implemented for the development of the gauge. The strain gauge orientation is as shown in Fig.4a. As shown in Fig. 4b, the cantilever beam is subjected to a vertical force (P) at a distance (Xg) away from the Strain gauge location R, which can also be represented by a moment (M). For elastic deformations of the beam, the stress-strain relationship will be governed by Hooke's Law:

Eb =