HIGH-PRECISION LOAD WEIGHT MEASUREMENT SYSTEM IN THE

VEHICLE BED

Moscow, 2014

High-precision load weight measurement system (WMS) in the vehicle bed is based on high-precision calibrated micromechanical sensors. The system allows defining the weight of the load in the vehicle bed when the vehicle stops within 30 seconds with a high accuracy (about 2.5-3%). High accuracy of weight measurement is achieved through the use of high-precision micromechanical sensors and specially developed algorithms for processing the results of measurements in onboard computer. The developed algorithms take into account the design features of the vehicle where the WMS is installed. WMS measurement results are displayed at onboard computer or can be transmitted to the client via a communication channel.WMS can operate in all weather conditions as well as under the impact of external factors.The basic configuration of WMS consists of three measurement sensors, terminal box and onboard computer with display (if a vehicle has a computer and a data transmission system, WMS may be connected to them). WMS design may vary individually for specific customer requirements. High-precision WMS sensors installed in vandal-proof casing are fixed by “cold welding” on the load frame of the vehicle without violating its integrity and at the same time providing a secure fit during vehicle movement on roads with poor road surface. At the suggestion of the customer an information tank, sensor system and onboard measurement system (OMS), designed to control the parameters of the vehicle online, may be integrated into the WMS. WMS and OMS are developed and protected by RF patents No. 2445586 and No. 113230 respectively.

1. Purpose of high-precision weight measurement system 1. For commercial vehicle manufacturers. Currently the commercial vehicles have no system that would provide recording of the basic vehicle operation conditions within a warranty period: the weight of cargo transported, speed rate, road surface condition, etc. It is well known that improper operation of vehicles, especially during the warranty period, may lead to technical malfunctions of the vehicle not through the fault of the manufacturer, but because of inappropriate operation (overload, driving over the prescribed speed limit with overload on roads with poor road surface, improperly chosen gear etc.). At the same time commercial vehicle manufacturers have no real information about the operating conditions of the vehicles, and so they are forced to perform or carry out warranty repairs or replacement under warranty on a damaged vehicle. Commercial vehicle manufacturer has to bear substantial losses due to the lack of WMS in vehicles’ composition, additionally equipped with OMS. To solve this problem we propose to install high-precision weight measurement systems with integrated OMS in series-produced vehicles, which are further connected to the required sensors (speed, gear, etc.) for the warranty period, as well as to install an information tank. The proposed solution will allow determining the weight of the load, which is located in the vehicle, recording the operating conditions and the condition of the vehicle: its speed, switched gear, the profile and condition of road surface along which the route of the vehicle passes, recording impacts on suspension, as well as other service information. Information recorded in the information tank at the request of the manufacturer can be transmitted online via the remote monitoring system that will allow tracking vehicle operation conditions online during the warranty period and identifying the main reasons leading to the technical malfunction. 2. For leasing companies.Installation of developed WMS together with OMS on vehicles owned by leasing companies will also solve the problem faced by the commercial vehicle manufacturers; insure themselves against unreasonable expenses for repair of vehicles, operated in violation of the operating conditions, or their replacement by new ones. In addition, the use of WMS together with OMS and on-board data transmission system connected online to the dispatch center will allow real-time monitoring of cargo being transported and vehicle operating conditions, and, if necessary, provide appropriate guidance to drivers. 3. For state authorities (customs, border service, road service and other Federal Services)The practical use of the developed WMS will significantly reduce the workload at points of Customs and Border Federal Services, providing the opportunity to get accurate online information about the weight of cargo actually

transported in the vehicle, and compare the information with the data presented in the accompanying documentation. The Federal Road Service, using WMS together with online data transmission system to the weighing points will allow getting accurate online information about vehicles’ load without stopping them, which will improve the system of control over the goods being carried, significantly reduce the workload at weighing points, as well as provide safety of main transportation routes especially during spring period when restrictions on the passage of heavy trucks are imposed on separate sections of the roadway. 4. For logistics companies.Installation of WMS with OMS and onboard data transmission system connected online to the dispatch centers of logistics companies will allow for remote control of the cargo, will provide a proper load in accordance with the requirements to vehicles, as well as real-time control of freight transportation, preventing excess loading and unauthorized unloading of vehicles. This system will significantly reduce the time of delivery, as the need to pass multiple weighing on fixed weighing machines along the route and the loss of time on waiting for the turn to be weighed will be eliminated. In the long term, after equipping all vehicles with WMS, stationary weighing points creating inconvenience to other cars on the routes at the locations of stationary weighing points, will be eliminated.

2. Main advantages of high-precision weight measurement system The preliminary study of various technical solutions for weighing cargo in the bed of the vehicle led to the following conclusions:1. Strain gauge sensor sensitivity is significantly lower than that of sensors based on micromechanical structures.2. Strain gauges provide low accuracy (over 15%) of evaluation of load weight in the vehicle bed and do not solve other problems mentioned in Section 1. Sensors based on micromechanical structures provide high accuracy (about 2-3%) due to the possibility of their high-precision calibration, and the use of original algorithms for calculating the weight of the load according to the results of high-precision measurement of vehicle frame deflection by three sensors mounted at the optimal points, the coordinates of which are calculated using specially developed mathematical models.3. In the weight measurement system based on strain gauges the sensing element is attached directly to the vehicle body. Therefore, during vehicle operation in adverse weather conditions the contact of the sensing element with the surface on which it is installed breaks, which leads first to the loss of precision and then to the loss of data accuracy. In the developed WMS based on micromechanical sensors the sensitive structure and the electronic unit for processing measurement results are located inside vandal-proof sealed enclosure, which is mounted on the frame of the vehicle by “cold welding” not affecting the integrity of the vehicle load frame.4. Service life of strain gauges’ sensitive elements is two orders of magnitude less than that of the sensitive structure of micromechanical sensors.5. Installation of strain gauges’ sensitive elements requires special preparation of the vehicle body surface and the use of a special adhesive. Mounting the sensor body on the basis of sensitive micromechanical structures is carried out using standard technology of “cold welding”.

3. Weight measurement system based on micromechanical sensitive structures

A block diagram of WMS based on micromechanical sensitive structures is shown in Fig. 1, and the appearance of WMS sensor, mounted on the frame of the vehicle, is shown in Fig. 2.

The format and procedure for data transmission from sensors to the onboard computer unit is determined by data communications protocol between the computer unit and the devices connected to it.Data communications protocol between the computer unit and the devices connected to it is provided by the Customer. Data transmission interface is CAN.The power supply of sensors is provided from the onboard vehicle network via built-in power source (supply voltage: 9 to 36 V, absorbed current is specified at the stage of delivery of an experimental batch).WMS shall be provided with two modes: calibration mode and weight measurement mode. Before performing weight measurement the system shall be calibrated. Calibration technique is given in the instruction manual for each vehicle type and can be adjusted according to the results of preliminary tests.

Load weight

information

Terminal box

Standard tilt gauge

Front tilt gauge

Front tilt gauge

Onboard unit

Fig. 1 Fig. 2

4. Onboard Measurement System A block diagram of onboard measurement system (OMS) is shown in Fig. 3 and its appearance is shown in Fig. 4.

Onboard Measurement System (OMS) is designed to control traffic parameters (efficiency factor) of the vehicle online and is designed for:

• collection of vehicle parameters, their initial processing, long-term storage, analysis, and subsequent transfer of the results to a remote centralized control panel or external storage device;

• determining the actual mileage and operating conditions of the vehicle;

• restoration of vehicle spatial course of movement by recorded data to analyze the causes of road accidents;

• determining the current location of the vehicle in case of theft.

MPU-6000 strapdown inertial unit

microSD memory card

SIM908 GPS/GSM module

LPC2478microcontroller

USB interface

USB interfaceSIMcard

GPS/GSM antennas

Fig. 3 Fig. 4

5. Reliability and service life of WMS and OMS as well as their resistance to external factors

Mean time between failures of WMS and OMS: at least 17,000 hours (operation mode - continuous).Mean life of WMS and OMS after the completion of preliminary bench tests: at least 15,000 hours.WMS and OMS characteristics and values of resistance to external mechanical and environmental factors are shown in Table 1.

Table 1.

Exposure factor Characteristics of exposure factor

Value of exposure

factor

Permissible variation of test modes standards

Sinusoidal vibration

Frequency range, Hz 10–70 ±1

Acceleration amplitude m/s2 (g) 39.2(4) ±2(0.2)

Duration of exposure, min 90

Mechanical shocks

During operation

Shock acceleration peak value, m/s2 (g) 147 (15) ±20%

Impact duration, ms 10

Number of shocks in each direction 1000

During transportation

Shock acceleration peak value, m/s2 (g) 250 (25) ±20%

Impact duration, ms 6

Number of shocks in each direction 4000

Reduced temperature

Operating temperature, °С –40 ±3

Limiting temperature, °С –55 ±3

Exposure time at each temperature, h 2

Elevated temperature

Operating temperature, °С +55 ±3

Limiting temperature, °С +55 ±3

Exposure time at each temperature, h 2

Humidity at elevated temperature in continuous mode

Relative humidity, % 93 ±3

Temperature, °С 40 ±3

Exposure time at each temperature, h 144

Moscow, 2014

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