ON ROAD FUEL CONSUMPTION MEASUREMENTS IN A TRUCK AT CONSTANT SPEED USING A TOWING TRAILER WITH ELECTROMAGNETIC BRAKE SIMULATING VARIED UPHILLS

Global warming is the subject of national and international policies and legislation. The importance of on road testing in commercial vehicles, under real conditions of application is therefore increasing. For the execution of the Diesel consumption tests under real conditions and reproducible, it is used a heavy truck and a towing trailer prototype with electromagnetic brake, object of several presentations and papers, including SIMEA 2015. Concerning this Prototype, Patent was required to INPI, a support by FAPESP got through a PIPE Project and an approval by the competent authorities for running on road was granted.


INTRODUCTION
Global warming is a subject of national and international policies and legislation [1], [2], [3], the Air Pollution especially in big cities is of real concern worldwide [4]. In Brazil, the emission legislation for Diesel was developed by PROCONVE and at present defines the emission limits according to CONAMA FASE 7, similar to Euro 5 in Europe [5]. The importance of energy savings is raising in all sectors; for example, passenger's cars, see PROGRAMA BRASILEIRO DE ETIQUETAGEM PBE [6]. The Brazilian Labelling Program (PBEV), was promoted and regulated by INMETRO by the Decree (Portaria) 544/12 [7] and supported in partnership with CONPET [8]. For light vehicles, the Labelling Program was implemented and Borges [9] reminders that a Labelling Program allows useful information to consumers about the performance, concerning to energy efficiency, fuel consumption and the emission of gaseous pollutants and greenhouse effect. Classification of fuel consumption for heavy vehicles was not implemented [10].
In Brazil, the government defined a new Program Rota 2030 [11], that will replace the Inovar-Auto [12] which will focus on the energetic efficiency of passenger cars. We can assume that for commercial vehicles, due to their importance, similar programs and legislations will also follow. Emissions and fuel consumption reduction are therefore both important objectives of the automotive industries, as pointed out by many authors, for example [13] and [14].
The importance of on road emission testing under real conditions of application is increasing. For on road testing of heavy trucks, it was developed by the authors a towing trailer prototype with electromagnetic brake, see Folder [15] and Attachment 1, object of several presentations and papers [16] and [17], including SIMEA 2015 [18] and Congresso SAE Brasil 2015 [19]. Concerning this Prototype, Patent was required to INPI [20], a financial support by FAPESP got through a PIPE Project [21] and an approval by the competent authorities for running on public roads was granted [22]. It is proposed with this towing trailer, to perform fuel consumption and in future, emission tests of heavy commercial vehicles.
There are several methods for fuel consumption measurements:  Measuring the fuel volume in the tank, for example by ultrasound or capacitive sensors [23].  Measuring the consumed fuel mass, for instance, in paper presented at SIMEA 2015 [24 ], that evaluates the influence of tires on fuel consumption. In that case, it was used a very precise analytical scale that weights an independent fuel tank, not connected with the vehicle tank.  Measuring the fuel consumption through CAN data of the Diesel engine [25].  Measuring the fuel flow to the engine and the fuel return to the tank [26] The Standard SAE J1321 201202 [27], revised on 20-12-06 defines a methodology for fuel consumption tests of trucks and buses over 10,000 lb on testing tracks and on roads. On road tests are offered as an alternative to lower costs compared to testing tracks, but with less accuracy due to the variable environmental (traffic) conditions. According to that Standard, evaluations the tests must be carried out under controlled conditions and with an extensive data collection and constraint analysis.

Development of the Prototype
There are no stationary installations with chassis dynamometers for testing heavy vehicles in Brazil, such as that one in Mahle [28], formerly Behr, in Germany, and some few others in the world. Due to that, the authors developed a Towing Trailer Prototype with electromagnetic brake for testing on road (roads and track's testing) heavy commercial vehicles, presented in the Folder [15], see also Appendix 1, with the history and features of the Towing Trailer. Optimizations were introduced and the external structure view also enhanced. Fig. 1 and 2 show the new aluminum plated side walls, doors and windows were also introduced.
The forces between truck and towing trailer are measured by strain gauge sensor, measurement of the electromagnetic braking torque was introduced based on strain gauges' sensor. The Towing Trailer Prototype was enhanced in its controls and optimized in the continuous setting of the electric current of the electromagnetic braking. The braking current is still controlled and regulated by wire in the cab. Fig. 3 and 4 shows the interior of the Prototype.     All those data are stored in the lap-top, example of a data sheet is presented in Appendix 2.

Auxiliary fuel tank
For measuring fuel consumption on road or on testing tracks, it was developed a device shown in Fig. 7 and 8 that allows initially to measure visually the fuel level (column of fuel). Capacitive fuel level measurements are ongoing and will be presented in future.  The system consists of a plastic reservoir with circa 8 liters, positioned at the level of the truck fuel tank (s) and fixed to a steel sheet structure, which is fixed on the truck chassis.
For short distances, the fuel level and the consumption can be measured by the fuel volume variation consumed in the auxiliary tank, which is not connected hydraulically to the truck fuel Capacitive sensor tank(s). By filling the auxiliary tank, it´s possible calibrate the auxiliary tank volume as a function of the level of the fuel column.

4.2.
Calibration of the fuel mass in the auxiliary tank The proposed system also intends to measure the fuel consumption through measurement of weight (mass) of the consumed fuel. The steel structure with the auxiliary tank is suspended laterally by a steel plate that is also set in a profile U and screwed in the truck frame. Strain gauge bridge was glued on this steel plate and weights the structure and the fuel mass by measuring the bending stress. Test with this system will be shown in next Chapel.

Measurement of the truck fuel volume
For consumption evaluation in longer distances, the system above explained can also be used, with the auxiliary tank connected hydraulically to the main tank(s). Due to the principle of communicating vessels, the auxiliary tank fuel level will be the same of the truck fuel tanks, if the truck is in a horizontal plane. The height of the fuel column gives an indication of the total fuel truck volume. By fulfilling the fuel tank (s) gradually, the truck fuel volume can be calibrated.

Fuel consumption measurements at 20 km/h
For performing Diesel consumption tests under real and reproducible conditions, it was used a heavy truck 6x4 with the Towing Trailer Prototype with electromagnetic brake. The weight of the truck was 13.830 kg, and the one of the Trailer was 14.080, the total weight of those vehicles was 29.910 kg.
Similar to the cooling tests described by the authors in [17,18], fuel consumption tests with a 6x4 heavy truck and the Towing Trailer Prototype were performed at constant speed of 20 km/h and several electromagnetic braking levels. The testing lap length was 1,7 km and the test time of each lap was almost the same. The road was plane with a roundabout in each extremity. Considering the testing costs, it was defined short test distances for each test, the purpose was to evaluate the methodology used and the sensitivity of the consumption measurements. This fuel consumption measurements use the auxiliary tank of circa 8 liters and is hydraulically independent of the main (s) truck fuel tank (s). For longer distances, the auxiliary fuel tank volume should be bigger. For measurements till 80 km, similar to Standard SAE J1321, should be with auxiliary tank hydraulically integrated to the main truck tank and will be presented in future, in other paper.
The test laps were initially repeated 3 times without electromagnetic braking current, to evaluate the repeatability of the consumption data. The laps were then repeated with 2 and 5,0 A each, as shown in Table 1.
The average consumption of the 3 LAPS without electromagnetic braking was set a value of 100%. The consumption values for 2 and 5,5 Amperes presented an increasing of respectively 39 and 140 %. Without current, the engine runs at partial load, with elevated currents, the engine runs near the top limit.  Fig. 9 shows the measurements of 25.05.2017, consisting in the present data of time, testing time, temperatures, traction forces, braking and current level, batteries voltages. Diagrams of temperatures, traction forces and speed along the whole test are shown. The electromagnetic braking torque as well the fuel consumption is not indicated in the diagrams and will be discussed in next chapter.

Worksheets
The measured data can be assessed in the worksheets, for example (extract) in Appendix 2 and be transformed in diagrams as shown in Fig. 10 to 19. In Appendix 2, an extract of the laptop desktop shows momentanes measured data and other curves during the testing time:  Present values of hour, date, vehicles speed received from the GPS.  Curves of temperatures, batteries voltage, rotation and current from electromagnetic brake system.  Curves of traction forces, braking torque and fuel level on the auxiliary tank gotten through the developed strain gauges' sensors.
During de tests the Electromagnetic Brake (EMB) control data was measured and registered like the example shown in Figures 7 to 12 EMB Rotation (Fig 8), Temperatures (Fig. 10) and Batteries Voltage (Fig. 11) are used to control the function of the EMB system. The curves indicate the relationship between the EMB current (9) and the EMB torque (10) and the possibility to measure those variables A former static calibration of the torque performed with a manual lift and an analogic dynamometer indicated a value of 0,210 mV/V for a force of 5000 N and a lever of 0,2 m, resulting in a torque of 1.000 Nm. The EMB torque by a current of 5,0 A corresponds to 4,88 mV/V.

GPS measurements
The GPS in the truck cab roof sends the data to the laptop. The present time, testing time and speed are indicated on the laptop screen. The speed during the whole test is shown in a curve. The latitude and the longitude from worksheet as well the speed can be transformed in curves as shown in Fig. 10, 11 and 12. Fig. 13 present the test route obtained from latitude and longitude. In Fig. 12 the lap of 1.7 km with the two roundabouts, can be seen.      The electronic torque measurement developed through a strain gauges bridge presented good results. Fig. 18 shows the result of the static calibration of this system performed by a manual lift and an analogic force dynamometer. Measurements realized on other on-road test conditions show a very good result of this system and could confirm the relationship from electromagnetic braking current, see Fig. 19.
A previous static calibration of the torque performed with a manual lift and an analogic dynamometer indicated a value of 0,210 mV/V for a force of 5000 N and a lever of 0,2 m, resulting in a torque of 1.000 Nm. The EMB torque by a current of 5,0 A corresponds to 4,88 mV/V. 5.6. Consumption electronic measurement It was proposed to measure the fuel consumption by measuring the fuel column in an auxiliary tank. This fuel level (fuel column) was calibrated in function of the fuel volume in the auxiliary tank. The electronic consumption level was measured by the strain gage sensor and calibrated in function of the fuel level column, the fuel volume and the fuel mass in the auxiliary tank. This static calibration was possible as shown in Fig. 20 although the tendency for vibration/oscillation of the auxiliary tank suspension. Fig. 21. Consumption measurement at 20 km/h. At standstill, it is possible to measure the fuel level The measurement of the consumption should be done presently on standstill vehicles. In future, the steel sheet suspension of the auxiliary tank (with the strain gauges) could be reinforced and /or the electronic signal could be filtered for higher oscillation signals. km/h performed with the independent auxiliary fuel tank showed a good performance for short test distances. 4. The used independent auxiliary fuel tank (8 liters) is too small to perform consumption longer distance measurements. 5. Measurement of the fuel level and the fuel consumption with the independent auxiliary tank by weighting the mass through the strain gauge system shows a possibility of evaluations in short distances. Oscillations must be reduced or suppressed.

CONCLUSIONS
 The authors, based on the tests, considered that the use of a towing trailer and semitrailer will rise in importance in fuel consumption and emission tests during future developments of commercial vehicles, although references in literature on that matter were not found.  On-road tests in varied slopes and speeds performed with the auxiliary fuel tank connected with the truck tank and rigidly fixed on the truck chassis will allow fuel consumption measurements for longer distances.  Development of measurement of fuel level by a capacitive sensor is ongoing and the tests should be completed in different speeds and electromagnetic brake conditions.  In future tests of on-road fuel measurements with towing trailer, should be considered the use of devices with higher precision like the ones using CAN or fuel mass flow.  In future, real driving test conditions with the Towing Trailer Prototype can be extended to emission evaluations.  Tests should be continued with participation of commercial vehicles and systems manufacturers, to introduce those innovative procedures in Brazil. Support of FAPESP and other government institutions will be very important.
Background: Since the Decade of 70´s, on road tests to evaluate the thermal performance of cooling systems of commercial vehicles, are very complicated, several trucks are required to perform them. Stationary installations with chassis dynamometers and big fans were not feasible in Brazil due to the high costs.

Trailer Mounting:
In 2011 studies were initiated for a tower trailer to simulate uphill tests. The Prototype was mounted using a second-hand sugar cane trailer. It was installed an electromagnetic brake with electrical supply and control systems, gearbox, clutch, rear axle with differential and drive shaft system for transmission of the braking torque. Tests on the road: The Towing Trailer shows easy coupling to tractor truck, great application flexibility, the convoy has a good maneuverability and safety, even on not pavemented roads. The Trailer also has a high mechanical resistance, since its components are normally used in the heavy work in sugar cane crops. Weight limits of trucks for testing on public roads are dictated by legislation. For buses and agricultural tractor testing´s, the traction rod can be lowered. Testing limits: The initial braking power was increased by optimizing the layout, the electromagnetic brake cooling and power supply system. Cooling tests are possible (usually at 20 km/h) for vehicles up to 250 HP. Also, possible on road tests up to 90 km/h and higher potencies, in accelerated durability tests of powertrain, tires and other components as well as fuel consumption tests.
Electro Electronics: A control cabin on the front of the trailer brings together all the electric and electronic measurements and system controls and sends and receives Wi-Fi the information to a laptop placed in the cab of the tractor truck. The forces between tractor truck and trailer are measured by a specially developed sensor with strain gauges and sent also the signals to the laptop. New system based on strain-gauges was also developed for measuring the electromagnetic braking torque. The command and control during testing can be performed in the cab of the tractor vehicle and the Wi-Fi data, registered as showed in the figures below. Data can be logged on datasheets and allow the elaboration of graphics.

Advantages:
The towing trailer can be monitored in the cab of the tractor by the technician who performs the measurements and can also easily adjust the braking power. There is no need for other trucks and drivers, reducing the costs of the tests. Easy maneuverability, can travel on public roads, observed the weight legislation limits.

Developments:
The developments had initially a partial support of FAPESP, through the PIPE Project 2012/50992-7. Testing and incremental developments in commands and other items are in progress, including fuel consumption, using a capacitive sensor for measurement of the fuel level. Development of a towing semi-trailer for testing trucks with higher power is planned as well consumption measurements with different methodologies.