# POWER TAKE OFF CYCLE DEVELOPMENT AND TESTING

FINAL REPORT

SwRI ® 

### Project No. 03.15777.14

Prepared for:

Environmental Protection Agency 26 West Martin Luther King Drive Cincinnati, OH 45268

Prepared by:

Joseph W. Anthony, Senior Research Engineer Janet Buckingham, Staff Analyst Ashok Nedungadi, Principal Engineer Joe Steiber, Principal Engineer

Glen Wendel, Staff Engineer

September 2010

# POWER TAKE OFF CYCLE DEVELOPMENT AND TESTING

FINAL REPORT

SwRI ® 

### Project No. 03.15777.14

Prepared for:

Environmental Protection Agency 26 West Martin Luther King Drive Cincinnati, OH 45268

September 2010

Prepared by: Approved by:

______________________________ _________________________________ Joseph W. Anthony Jayant Sarlashkar Senior Research Engineer Manager Department of Engine and Vehicle R&D Department of Engine and Vehicle R&D

DEPARTMENT OF ENGINE AND VEHICLE R&D ENGINE, EMISSIONS AND VEHI CLE RESEARCH DIVISION

This report shall not be reproduced, ex cept in full, without the written approv al of Southwest Research Institute ®

. Results and discussion given in this report relate only to the test items described in this report.FINAL REPORT 03-15777.14 ii TABLE OF CONTENTS Page

LIST OF FIGURES ............................................................................................................... ....... iii LIST OF TABLES ................................................................................................................ ........ iv 1.0 INTRODUCTION ............................................................................................................ 1 2.0 TASK 1 - INITIAL RESEARCH IN FIELD .................................................................... 2 3.0 TASK 2 - APPLIED PTO RESEARCH ........................................................................... 3 4.0 TASK 3 - DUTY CYCLE ANALYSIS ........................................................................... 10 5.0 TASK 4 - DUTY CYCLE DEVELOPMENT .................................................................. 31 6.0 TASK 5 - TEST RIG RESEARCH AND DEVELOPMENT ......................................... 35 7.0 SUMMARY .................................................................................................................. ... 38

..FINAL REPORT 03-15777.14 iii LIST OF FIGURES Figure Page

1 Utility Truck Used for In-Use Data Logging .................................................................4 2 Flow Meter and Pressure Transduc er Installed on Utility Truck ...................................4 3 Example of Data Recorded from Utility Truck ..............................................................5 4 An Example of an Automated Side Loader (ASL) Refuse Truck ..................................6 5 PTO Driven Pumps for ASL Refuse Truck ....................................................................7 6 Flow Meter and Pressure Transducer In stalled on Inlet to Loader Valve Body for ASL Refuse Truck ....................................................................................................7 7 Flow Meter and Pressure Transducer In stalled on Inlet to Compactor Valve Body for ASL Refuse Truck ....................................................................................................8 8 Example of Loader Data Reco rded from ASL Refuse Truck .........................................8 9 Example of Compactor Data Reco rded from ASL Refuse Truck ...................................9 10 Example of Engine Speed and Vehicle Speed Data Recorded from ASL Refuse Truck ..................................................................................................9 11 Utility Truck Pump Pressure Relative Frequency Histogram for PTO “ON” Operation During Rural Testing ...................................................................................12 12 Utility Truck Pump Pressure Relative Frequency Histogram for PTO “ON” Operation During Urban Testing ..................................................................................16 13 Refuse Truck Compactor Pressure Relati ve Frequency Histog ram for PTO “ON” Operation When Only the Co mpactor was Operating ..................................................21 14 Refuse Truck Loader Pressure Relati ve Frequency Histogr am for PTO “ON” Operation When Only the Loader was Operating ........................................................23 15 Refuse Truck Compactor Pressure Relati ve Frequency Histog ram for PTO “ON” Operation When Both Compactor and Loader Were Operating ..................................26 16 Refuse Truck Loader Pressure Relati ve Frequency Histogr am for PTO “ON” Operation When Both Compactor and Loader Were Operating ..................................26 17 Cluster Analysis Means for Refuse Tr uck when Both Loader and Compactor Were Operating Using Selected Data ...........................................................................29 18 FFT Plot for Refuse Truc k Compactor Operation ........................................................32 19 FFT Plot for Refuse Truck Loader Operation ..............................................................32 20 Hydraulic System Simulator Circuit Schematic ...........................................................35

..FINAL REPORT 03-15777.14 iv LIST OF TABLES Table Page

1 Utility Truck Configuration ...............................................................................................3 2 Refuse Truck Configuration ..............................................................................................6 3 Definitions of PTO Operati on for the Utility Truck ........................................................10 4 Time at Various Operating Conditions for Utility Truck Rural Testing .........................11 5 Pump Pressure Percentiles for Time at PTO “ON” Operation for Utility Truck Rural Testing ................................................................................................................ ...13 6 Steady-State Modes for Rural Utility Truck Cycle .........................................................13 7 Time at Various Operating Conditions for Utility Truck Urban Testing ........................15 8 Pump Pressure Percentiles for Time at PTO “ON” Operation for Utility Truck Urban Testing ................................................................................................................ ..16 9 Steady-State Modes for Urba n Utility Truck Cycle ........................................................17 10 Definitions of PTO Operat ion for Refuse Truck .............................................................18 11 Time at Various Operating Conditions for Refuse Truck Testing ..................................19 12 Compactor Pressure Percentiles for Ti me When Only The Compactor was in Operation for Refuse Truck Testing ................................................................................22 13 Cluster Analysis Results for Compactor Only PTO “ON” Operation for Refuse Truck ........................................................................................................................ .......22 14 Loader Pressure Percentiles for Time Wh en Only Loader was in Operation for Refuse Truck Testing ......................................................................................................24 15 Cluster Analysis Results for Loader Only PTO “ON” Operation fo r Refuse Truck ......25 16 Compactor and Loader Pressure Percen tiles for Time When Both were in Operation for Refuse Truck Testing ................................................................................27 17 Percent of Total Time at Compactor and Loader Pressure When Both are Operating for the Refuse Truck .......................................................................................27 18 Cluster Analysis Results for Both Compactor and Loader PTO “ON” Operation for Refuse Truck Using Selected Data ...........................................................29 19 Final Steady-State Modes for Both Compactor and Loader PTO “ON” Operations for the Refuse Truck Using all Data .............................................................30 20 Composite 10-Minute Cycle Times by Vehicle and Application ...................................31 21 Composite 10-Minute Cycle Times for Each Mode .......................................................33 22 Final Composite 10-Minute PTO Duty Cycle .................................................................34FINAL REPORT 03-15777.14 1 of 38 1.0 INTRODUCTION

In an effort to evaluate and address the impacts of Power-Take-Off (PTO) for engine performance, the Environmental Protection Ag ency (EPA) requested Southwest Research Institute (SwRI) to evaluate engine and vehicle performance of utility vehicles and refuse haulers for boom operation; particularly where power demands are associated with use of these implements. It is essential to be able to charac terize the needs of the conventional as well as the alternative hybrid designs on a consistent basis. To that e nd, background research was conducted to determine which vehicles were most likely to be fitted with hybrid PTO systems. Data were collected to determine the operating regime to de velop the appropriate du ty cycle to assess PTO operation overall. A test rig was designed for properly exerci sing these vehicle components.FINAL REPORT 03-15777.14 2 of 38 2.0 TASK 1 - INITIA L RESEARCH IN FIELD

A literature review of on-highway truck appl ications utilizing power take-off (PTO) (by vehicle class and use) was conducte d in order to characterize the operations that require the use of PTO. The literature search focused on the following topics.

o Existence of available duty cycles representative of PTO operation

o Engine parameters including speed, torque, and fuel consumption during PTO operations

o PTO hydraulic pressure and flow

o Estimates of annual sales volumes for each type of application of PTO equipment

o Available test rigs

Potential for the adoption of hybrid power systems in these applications and their effects during PTO operation, including reductions in energy consumption an d GHG emissions were also considered.

The literature search spanned technical contributions from th e past ten years and focused on PTO duty cycles for both conventional and hybrid powertrains. Although, hybrid PTO systems have been implemented on utility truck fo r many years, a search of the most recent SAE and pertinent technical papers on the subject of PTO operations fo r a variety of on-road vehicle classes resulted in the following two papers,

H. C.Frey, K. Kim, Comparison of Real -World Fuel Use and Emissions for Dump Trucks Fueled with B20 Biodies el Versus Petroleum Diesel, 85 th Annual Meeting of the Transportation Research Board , 2006

SwRI, 2007. Southwest Research Institute. Emissions and Fuel Economy Testing of Three Utility Trucks. SwRI Project No. 03.11602. March 9, 2007.

The search included annual sales volumes for as many PTO-equipped vehicle groups as the schedule allowed with conc entration on vehicles with large volume sales in 2011 and beyond. However, these data are not, generally, made public by any of the manufacturers or trade associations. During the literature search , industry contacts were consulted to determine which vehicles were most likely to be hybridized in large volumes. Two major applications were cited as being candidates, utility boom trucks (utility) and auto mated side loader (ASL) refuse trucks. It is generally accepted that there are approximately 150,000 utility boom trucks in operation in the United States and approximately 100,000 refuse tr ucks in operation, of which 20,000 are ASL-type refuse trucks. Base d on recommendations from manufacturers and engineering judgment, it was deci ded to instrument util ity boom trucks and ASL refuse trucks. The utility trucks were chosen due to their propen sity for hybridization and their large fleet size. ASL refuse trucks were chosen despite their cu rrent, relatively small population because it is projected that they will become increasingly co mmon as municipalities continue to switch to automated pick-up to reduce labor costs. Manuf acturers also indicated that there are plans to develop hybrid PTO systems for ASL trucks in the near future.FINAL REPORT 03-15777.14 3 of 38 3.0 TASK 2 - APPLIED PTO RESEARCH

The objective of this task was to quantif y PTO work during PTO operations and the percentage of time that PTO operations take plac e in a one-day time frame for the various classes of vehicles considered in Task 1. The data coll ected was used to develop a composite PTO duty cycle that can serve to compare the fuel efficiency of one vehicle over the other as well as define the design parameters for the construction of a PTO test rig.

From Task 1, it was determined that utility ae rial boom trucks and refuse trucks were the most likely applications for hybrid PTO systems due to their PTO duty cycle. It was originally planned to combine in-use field data loggi ng with existing data from PTO and truck manufacturers, but no existing data were made available for this project.

SwRI obtained one utility boom truck and one refuse truck to instrument for data collection while in-use. The utility truck was a 2008 Ford F- 750, Figure 1, was equipped with a Caterpillar C7 diesel engine, an automatic Allison five-speed transmission, and Eaton PTO and pump. The specifications of this truck are listed in Table 1. A turbine-style flow meter and a pressure transducer were installed on the outle t side of the hydraulic pump to allow the pump flow and pressure, shown in Figure 2. The truck’s J1939 CAN comm unication was used to record vehicle speed, engine spee d, engine fuel rate, and engine load. An example of the data recorded is shown in Figure 3. Together, these data were used to determine the amount of time the PTO was used compared to the amount of time the vehicle was in operation. The utility truck was operated for a total of four week s, two weeks each in two different geographic locations, urban and rural, for this project.

TABLE 1. UTILITY TRUCK CONFIGURATION

Vehicle 2008 Ford F-750 VIN 3FRXF75T99V100971 Engine Caterpillar C7 Emission controls EGR, DPF Rated power, hp 250

Transmission Allison Automatic, 5-speed

GVWR, lb 33,000 PTO Pump Eaton, 14 gpm@700 RPMFINAL REPORT 03-15777.14 4 of 38 FIGURE 1. UTILITY TRUCK US ED FOR IN-USE DATA LOGGING

FIGURE 2. FLOW METER AND PRESSURE TRANSDUCER INSTALLED ON UTILITY TRUCKFINAL REPORT 03-15777.14 5 of 38 FIGURE 3. EXAMPLE OF DATA RECORDED FROM UTILITY TRUCK

It was decided to instrument an Automated Side Loader (ASL) refuse truck for this project since they are becoming more popular and have a higher PT O load than traditional rear load refuse trucks. Due to prop rietary concerns, a photograph of th e actual test truck is not in this report. Figure 4 shows a gene ric ASL refuse truck. The truc k instrumented for this project was a 2010 Mack equipped with a Mack 10L diesel engine and an Allison automatic 5-speed transmission. The specifications for this truc k are shown in Table 2. The ASL truck has two hydraulic pumps for each of the two hydraulic circ uits, Figure 5. One circuit is for the side loader arm and the other is for compaction. Traditional rear lo ad refuse trucks only have a compaction circuit. Each hydraulic circuit was in strumented with a turbine-style flow meter and pressure transducer, however, due to packagi ng constraints, the flow meter and pressure transducer for each circuit was mounted at the in let of the valve body controlling the flow to each circuit’s actuators. Although it may have been preferable to measure the pressure at the pump’s outlet, it was assumed that the pressure drop in the lines was neg ligible. Figure 6 shows the flow meter and pressure transducer for the loader arm and Figure 7 shows the flow meter and pressure transducer for the compactor. As wi th the utility truck, the ASL truck’s J1939 CAN communication was used to record vehicle speed, engine speed, e ngine fuel rate, and engine load. 0 500 1000 1500 2000 2500 3000

0 10 20 30 40 50 60 70 80

5000 5500 6000 6500 7000 7500Pressure,psi&EngineSpeed,rpmFlow,gal/min&VehicleSpeed,kph

Time, seconds Pump flow

Vehicle speed

Pump pressure

Engine speedFINAL REPORT 03-15777.14 6 of 38 FIGURE 4. AN EXAMPLE OF AN AUTOMATED SIDE LOADER (ASL) REFUSE TRUCK

TABLE 2. ASL REFUSE TRUCK CONFIGURATION

Vehicle 2010 Mack VIN 1M2AU02C6AM004642 Engine Mack MP7-405M Emission controls EGR, DPF Rated power, hp 405

Transmission Allison 4500 RDS

GVWR, lb 56,000
PTO Pump Arm: Parker, 16 gpm@700 RPM Compactor: Parker, 23 gpm@700 RPMFINAL REPORT 03-15777.14 7 of 38 FIGURE 5. PTO DRIVEN PUMPS FOR ASL REFUSE TRUCK

FIGURE 6. FLOW METER AND PRE SSURE TRANSDUCER INSTALLED ON INLET TO LOADER VAL VE BODY FOR ASL REFUSE TRUCKFINAL REPORT 03-15777.14 8 of 38 FIGURE 7. FLOW METER AND PR ESSURE TRANSDUCER INSTALLED ON INLET TO COMPACTOR VALVE BODY FOR ASL REFUSE TRUCK

The added signals reduced the data sampling rate from 1 Hz to 0.5 Hz. The reduced sampling rate was acceptable for this work. The ASL truck was instrumented for two weeks of calendar time, however, due to a failed pre ssure transducer, accidental damage, and two connector failures, there were only five days of usable data. Figures 8 through 10 are examples of data recorded from the ASL truck.

FIGURE 8. EXAMPLE OF LO ADER DATA RECORDED FROM ASL REFUSE TRUCK 0 5 10 15 20

10350 10370 10390 10410 10430 10450 10470 10490 Time, secondsFlow, gal/min

0 500 1000 1500 2000 2500Pressure, psi Loader flow Loader pressureFINAL REPORT 03-15777.14 9 of 38 FIGURE 9. EXAMPLE OF CO MPACTOR DATA RECORDED FROM ASL REFUSE TRUCK

FIGURE 10. EXAMPLE OF ENGINE SPEED AND VEHICLE SPEED DATA RECORDED FROM ASL REFUSE TRUCK 0 5 10 15 20 25 30 35 40 45 50

10350 10370 10390 10410 10430 10450 10470 10490 Time, secondsFlow, gal/min

0 500 1000 1500 2000 2500Pressure, psi Compactor flow Compactor pressure

0 5 10 15 20 25 30

10350 10370 10390 10410 10430 10450 10470 10490 Time, secondsVehicle Speed, kmh

0 200 400 600 800 1000 1200 1400 1600 1800 2000Engine Speed, rpm Vehicle speed Engine speedFINAL REPORT 03-15777.14 10 of 38 4.0 TASK 3 - DUT Y CYCLE ANALYSIS

Data collected for the Task 2 database were used to determine individual representative duty cycles for PTO work for th e utility boom truck and the AS L refuse truck. Only data pertinent to the operation of the PTO were used in the duty cycles. Analyses of the data collected for the utility truck and the refuse truck are described in the sections below.

4.1 Utility Boom Truck Duty Cycle

Data collected during Task 2 for the util ity truck cycle development consisted of hydraulic pump pressure (psi) a nd pump flow (gal/min) versus time (seconds). Utility truck operations were performed in a rural environmen t (San Antonio) and in an urban environment (Fort Worth). Data from both of these environm ents were combined to produce one individual utility truck cycle. For the purposes of the cycl e development, data were selected only during the component operation when the truck was not moving (i.e, vehicle speed = 0). In addition, pump flow and pump pressure conditions were also an alyzed in order to identify idle and PTO operations. Table 3 lists the defini tions of the various PTO operations . If a single data recording resulted in the pump pressure ≥ 200 and the pump flow > 0, then the PTO was considered to be operating (i.e, “on”). PTO was considered “off’ if the pump pressure < 200 and the pump flow = 0. Data were not included in the duty cycle analyses for the PTO “off” condition. Lower pressures were considered to be within the ‘noi se’ of the instrumentation and do not reflect PTO operation even though they were re corded as non-zero. The noise was defined as any pressure value below the maximum reading with the PTO “off .” Two different situations represent idle periods. Idle 1 was defined when pump pressure was high but the pump was not flowing. Idle 2 was defined when there was low pump pressure (i.e., within the ‘noise’) but there was some pump flow. Note that almost all of the idle data collected on the utility truck in the rural setting met the criteria for Idle 1 (no pump flow).

TABLE 3. DEFINITIONS OF PTO OPERATION FOR THE UTILITY TRUCK

Pump Pressure, psi Pump Flow, gal/min 0 > 0
< 200 PTO Off Idle 2

≥ 200 Idle 1 PTO On

All the data collected for the utility truck operation in the rural setting were combined into one database wherein each second-by-second recording was identified by one of the four operating conditions outlined in Table 3. The data were then divided into ten separate key-on “events” which were defined by a gap in the cons ecutive time stamp during the data recording. This was done to examine continuous PTO operati ons. Table 4 summarizes the available utility truck data collected in the rural environment. Approximately 85% of the total data collected represented time when the vehicle speed = 0. Fo r purposes of the cycle development, 9.66% of the time was spent in PTO “on” operation wh ile 90.34% of the time wa s spent in the idle conditions.FINAL REPORT 03-15777.14 11 of 38 TABLE 4. TIME AT VARIOUS OPERATING CONDITIONS FOR UTILITY TRUCK RURAL TESTING

Events Total Test Time, sec Vehicle Speed = 0 PTO On Idle 1 Idle 2 PTO Off

Time (sec) at Pump Flow > 0 and Pump Pressure ≥ 200 Time (sec) at Pump Flow = 0 and Pump Pressure ≥ 200 Time (sec) at Pump Flow > 0 and Pump Pressure < 200 Time (sec) at Pump Flow = 0 and Pump Pressure < 200
1 197 35 124 0 38 2 1433 2 15 0 145 3 911 0 0 0 105 4 49191 8554 31090 685 1056 5 5786 248 2412 0 127 6 8000 1451 6082 0 69 7 22250 47 21151 0 29 8 29985 2340 21361 0 193 9 32507 68 28990 3 964 10 9578 8 7312 0 435 TOTAL 159838 12753 118537 688 3161 % Time at PTO On and Idle 9.66% 90.34%

Basic descriptive statistics and histograms of the collected pump pressure data over time were used to quantify the percentage of time various pressure levels were maintained. Scatterplots of pump pressure vs. time were al so generated in order to determine whether the duty cycle warranted a steady-state or transient characterization.

Figure 11 illustrates a relative frequency histogram of the pump pressure during the PTO ‘on’ operation for the utility truck te sted in the rural environment. Note that the pressure data are concentrated around 2400-2500 psi with a very small percentage of the pressures < 1000 psi.

Table 5 lists the cumulative percentiles of the pu mp pressure data for the rural utility truck testing. Approximately 90% of the pump pressure s lie between 2026.3 and 2575.6 psi (difference = 548.7 psi) while 80% of the pump pressures lie between 2324.7 and 2558.8 psi (difference = 234.1 psi). Since the range of pump pressure for th e PTO ‘on’ operation is within the expected variation of pre ssure at a constant PTO operati on for the utility truck, a single steady-state PTO ‘on’ mode was in vestigated to represent the util ity truck operation in the rural environment.FINAL REPORT 03-15777.14 12 of 38 Scatterplots of the pump pressure vs. time data also indicate d that the selection of a single operational mode was suitable sinc e the PTO ‘on’ conditions could be easily identified when the pump pressure was sustained and targeted near 2500 psi. Thus, the rural utility truck operation was defined using two stea dy-state modes (PTO ‘on’ and idle) as defined in Table 6. The pump pressure representing the PTO ‘ on’ condition was set to the aver age pump pressure during that operation. The statistical frequenc y analysis of the in-field data was used to determine the relative proportion of time allocated to each steady-state mode. Finally, the average pump pressure was normalized as a percentage of the maximum operating pump pressure rating for the pump used in the utility truck (3000 psi). The nominal operating pressure for the hydraulic pump is 2500 psi, but pressure varied depending on the load and spiked to higher values when the flow was interrupted abruptly. Thus, the PTO ‘on’ steady-state m ode would be run at 80.45% of the rated maximum pump pressure.

FIGURE 11. UTILITY TRUCK PUMP PRESSURE RELA TIVE FREQUENCY HISTOGRAM FOR PTO “ON” OP ERATION DURING RURAL TESTINGFINAL REPORT 03-15777.14 13 of 38 TABLE 5. PUMP PRESSURE PE RCENTILES FOR TIME AT PTO

“ON” OPERATION FOR UT ILITY TRUCK RURAL TESTING

Percentile, % Pump Pressure, psi 100 (max) 2920.90 95 2575.60 90 2558.80 80 2536.90 70 2519.30 60 2503.20 50 2486.40 40 2466.60 30 2443.20 20 2411.00 10 2324.70 5 2026.30 0 (min) 200.43

TABLE 6. STEADY-STATE MODES FO R RURAL UTILITY TRUCK CYCLE

Mode % Time at Mode Avg. Pump Pressure, psi Max Pump Pressure Rating, psi Normalized Avg. Pump Pressure, % 1 9.66 2413.53 3000 80.45 2 (Idle) 90.34 0 3000 0

The second set of data collected for the ut ility truck operation occurred in the urban setting in Fort Worth. Again, all the data were combined into one database wherein each secondby-second recording was identified by one of the four operating conditions outlined in Table 3. Between the rural and urban data collection the flow meter was replaced. This change resulted in a slight flow offset at zero flow. Th erefore, it was decided that a pump flow ≥ 1 gal/min would be used to as part of the PTO ‘on’ conditi on. The pump flow definition for the operating conditions was changed from 0 to 1 gal/min to reflect the lower volume flowmeter in the truck operating in the urban setting. The data were then divided into 46 separate key-on “events” which were defined by a gap in the consecuti ve time stamp during the data recording.

Table 7 summarizes the available utility truck data collected in the urban environment. Approximately 69% of the total da ta collected represented time wh en the vehicle speed = 0. For purposes of the cycle development, 49.89% of th e time was spent in PTO “on” operation while 50.11% of the time was spent in the idle and PTO ‘off’ conditions. This is drastically differentFINAL REPORT 03-15777.14 14 of 38 than the percentage of time calculated for the PT O ‘on’ condition during the rural testing period. The PTO ‘off’ data were included in this urban setting analysis because the operator in the urban environment performed more operations per day than the rural operator. In rural operation, the operator allowed the PTO to be engaged for l ong periods of time, sometimes several hours, producing high pressure and no flow and it was decided that this was unnecessary load that should not be considered for the cycle develo pment. In urban operation, there were high pressure events with no flow, but those events typically occu rred intermittently during normal operation.

Similar analyses used in the investigation of the rural utility truck data were again performed using the urban utility truck data. Basic descriptive st atistics and histograms of the collected pump pressure data over time were us ed to quantify the percen tage of time various pressure levels were maintained. Similarly, scatterplots of pump pressure vs. time were also generated in order to determine whether the dut y cycle warranted a steady-state or transient characterization. Figure 12 illustrates a relative frequency histogram of the pump pressure during the PTO ‘on’ operation for the utility truck tested in the urba n environment. Note that the pressure data are concentrated around 2500 psi with a very small percentage of the pressures < 2000 psi. These pressure data demonstrated sma ller variation than those collected in the rural setting. Table 8 lists the cumulative percentiles of the pump pressure data for the urban utility truck testing. Approximately 90% of th e pump pressures lie between 2351.79 and 2578.56 psi (difference = 226.77 psi) while 80% of the pump pressures lie between 2432.26 and 2566.85 psi (difference = 134.59 psi). Analogous to the conclusi ons made for the urban truck usage data, the range of pump pressure for the PTO ‘on’ operation is within the expe cted variation of pressure at a constant PTO operation for the utility truck; therefore, a single stead y-state PTO ‘on’ mode was used to represent the utilit y truck operation in the urban envi ronment. This was confirmed in the scatterplots of the pump pressure vs. time data which also indicated that the selection of a single operational mode was suita ble since the PTO ‘on’ conditi ons could be easily identified when the pump pressure was sustained and targeted near 2500 psi. Thus, the urban utility truck operation was defined using two st eady-state modes (PTO ‘on’ and idle+PTO ‘off’) as defined in Table 9. The pump pressure representing the PT O ‘on’ condition was set to the average pump pressure during that operation. The statistical freque ncy analysis of the in-field data was used to determine the relative proportion of time allocated to each steady-state mode. Finally, the average pump pressure was normalized as a percentage of the maximum operating pump pressure rating for the pump used in the utility truck (3000 psi). Thus, th e PTO ‘on’ steady-state mode would be run at 83.47% of the rated maximu m pump pressure, which is very close to the normalized pressure computed for the PTO ‘on’ steady-state mode in the rural setting.FINAL REPORT 03-15777.14 15 of 38 TABLE 7. TIME AT VARIOUS OPERATING CONDITIONS FOR UTILITY TRUCK URBAN TESTING

Events Total Test Time, sec Vehicle Speed = 0 PTO On Idle 1 Idle 2 PTO Off Time (sec) at Pump Flow ≥ 1 and Pump

Pressure ≥ 200 Time (sec) at Pump Flow < 1 and Pump

Pressure ≥ 200 Time (sec) at Pump Flow ≥ 1 and Pump

Pressure < 200 Time (sec) at Pump Flow < 1 and Pump

Pressure < 200 1 37 13 3 0 21 2 868 0 0 0 90 3 1939 0 0 0 575 4 135 0 0 0 25 5 2091 0 0 0 23 6 348 0 0 0 348 7 3706 0 0 0 585 8 99 0 0 0 50 9 3531 0 0 0 235 10 3279 0 0 0 8 11 997 0 0 0 70 12 5700 0 0 0 111 13 98 0 0 0 51 14 105 0 0 0 38 15 60 0 0 0 31 16 1369 0 0 0 42 17 1039 0 0 0 107 18 39 0 0 0 6 19 590 0 0 0 69 20 1497 0 0 0 247 21 54 0 0 0 6 22 20 6 1 0 12 23 35 0 13 0 22 24 324 321 1 0 1 25 43 40 2 0 1 26 180 177 3 0 0 27 207 126 23 0 3 28 1722 1371 15 0 210 29 218 0 0 0 154 30 1837 78 28 40 1691 31 296 0 0 4 229 32 89 0 0 0 27 33 2605 0 0 3 1127 34 527 0 0 0 121 35 22941 13485 72 3 3707 36 455 206 31 3 215 37 5920 0 0 0 3014 38 30812 19820 129 4 5482 39 34188 17587 96 104 10351 40 5161 2757 37 5 491 41 36693 9913 89 4 17955 42 23146 5037 70 1 11367 43 16515 6322 19 3 5895 44 5925 1388 32 0 3001 45 30509 10767 34 3 10035 46 11776 343 31 3 11399 TOTAL 259725 89757 729 180 89248

% Time at PTO On and Idle 49.89% 50.11%FINAL REPORT 03-15777.14 16 of 38 FIGURE 12. UTILITY TRUCK PUMP PRESSURE RELA TIVE FREQUENCY HISTOGRAM FOR PTO “ON” OPE RATION DURING URBAN TESTING

TABLE 8. PUMP PRESSURE PE RCENTILES FOR TIME AT PTO “ON” OPERATION FOR UTILITY TRUCK URBAN TESTING

Percentile, % Pump Pressure, psi 100 (max) 2963.33 95 2578.56 90 2566.85 80 2555.88 70 2548.56 60 2541.98 50 2534.67 40 2526.62 30 2514.92 20 2486.39 10 2432.26 5 2351.79 0 (min) 236.28FINAL REPORT 03-15777.14 17 of 38 TABLE 9. STEADY- STATE MODES FOR URBAN UTILITY TRUCK CYCLE

Mode % Time at Mode Avg. Pump Pressure, psi Max Pump Pressure Rating, psi Normalized Avg. Pump Pressure, % 1 49.89 2504.14 3000 83.47 2 (Idle) 50.11 0 3000 0

4.2 Refuse Truck Duty Cycle

Data collected during Task 2 for the refu se truck cycle development consisted of hydraulic pump pressure (psi) a nd pump flow (gal/min) versus time (seconds). All the refuse truck operations were performed in a residentia l environment in Conroe , TX. For the purposes of the cycle development, data collected duri ng the driving times of the refuse truck in association with the refuse dump facility and driving times between residential areas were excluded from the analyses. The PTO is always in operation on this type of vehicle as the PTO pumps are coupled to the engine’s crankshaft. In discussion with EPA personnel it was decided to distinguish between driving and PTO operation. Therefore, data colle cted when truck is driving to and from fleet garage and to and fr om the landfill was excluded from the idle time of the PTO operation. Recall from Task 2 that the re fuse truck recorded pressure and flow for two separate hydraulic loops instead of a single loop as was the case with the utility truc k. One loop operated a side loader and the other loop opera ted the compactor. Thus, it was possible to examine the data under four different PTO opera ting conditions: (1) both the compactor and loader worked simultaneously, (2) compactor on ly, (3) loader only, and (4) both compactor and loader at idle.

Pump flow and pump pressure c onditions were analyzed in order to identify idle and the PTO ‘on’ operations. During the data analysis, it was discovered that the loader and compactor pressures appeared lower than expected. It was found that th e calibration gains were not updated in the acquisition program for the transducers inst alled on the refuse truck. The original data acquisition program was calibrate d for transducers operating from 0-5VDC instead of 1-5VDC, for the same pressure range of 0 to 3000 psi. This re sulted in the compactor and loader pressures being recorded with the wrong transfer functi on. The issue was resolv ed by re-scaling these pressure data by 1.25 during post-processing.

Table 10 lists the definitions of idle and PTO ‘on’ for the refuse truck. These flow and pressure definitions applied for both the compact or and loader. If a single data recording resulted in the pump pressure ≥ 150 and the pump flow ≥ 2, then the PTO was considered to be operating (i.e, “on”). These thresholds were sli ghtly above the typical va lues of the transducers when each pump was known to be off. Alternativ ely, PTO was considered in idle mode if these criteria were not met. Three different situations represent idle periods. Idle 1 was defined when pump pressure was high but the pump flow was very low. Idle 2 was defined when there was low pump pressure (i.e., within the ‘noise’) but pump flow was above the noise. Lastly, Idle 3 was defined as both very low pressure and flow . For the duty cycle development analyses, all three idle conditions were comb ined as one idle definition.FINAL REPORT 03-15777.14 18 of 38 TABLE 10. DEFINITIONS OF PTO OPERATION FOR REFUSE TRUCK

Pump Pressure, psi Pump Flow, gal/min

< 2 ≥ 2

< 150 Idle 3 Idle 2

≥ 150 Idle 1 PTO On

All the data collected for the refuse truck operation were combined into one database. Unlike the data collected during the utility truck phase, the refuse truck recorded data in 0.5 Hz or every 2 seconds instead of every 1 second. Thus, each data observation represents a twosecond interval. However, frequency counts and percentage of total time calculations are not influenced by the amount of time each recorded observation represents. For that reason all the tables represented in this section are the actual number of data observations and not the actual time elapsed during the data collection. Each tw o-second recording was identified by either the idle condition or the PTO ‘on’ ope rating condition outlined in Table 10. Also different from the utility truck data, the refuse data were not di vided into separate key-on “events” because the operation of the truck was continuous once it arrived at a residential area.

Table 11 summarizes the refuse truck data colle cted by the various op erating conditions. For purposes of the refuse truck cycle developm ent, 22.01% of the time wa s spent in the loader only PTO ‘on’ operation, 25.96% of the time wa s spent in the compactor only PTO ‘on’ operation, and 20.07% of the time was spent when both the compactor and the loader were operating in the PTO ‘on’ condition. Idle c onditions comprised 31.96% of the total available time.

Since the refuse truck data consisted of pre ssures from two independent loops (compactor and loader), the analysis to gene rate representative duty cycles was more complicated. Each of the three PTO ‘on’ operations was analyzed separate ly to obtain duty cycles and then they were combined to represent the refuse truck cycle. It was decided that a multi-mode steady-state duty cycle for each PTO ‘on’ operation would be explored and that a systematic repetition of these modes could simulate the cyclic operation of th e refuse truck, especially with the loader operation.FINAL REPORT 03-15777.14 19 of 38 TABLE 11. TIME AT VARIOUS OPERATING CONDITIONS FOR REFUSE TRUCK TESTING

Day Total Available PTO Test Time, sec PTO Operation Both Compactor and Loader: Time (sec) at Pump Flow ≥ 2 and Pump Pressure ≥ 150 PTO Operation Compactor Only: Time (sec) at Pump Flow ≥ 2 and Pump Pressure ≥ 150 PTO Operation Loader Only: Time (sec) at Pump Flow ≥ 2 and Pump Pressure ≥ 150 Idle for Both Compactor and Loader 1 12525 3089 2958 3137 3341 2 a 37000 0 0 0 0 3 24145 4425 6241 5400 8079 4 38915 7775 10227 8163 12750 5 7468 1377 2135 1583 2373 Total Time 83053 16666 21561 18283 26543 Actual Time, hr 46.14 9.26 11.98 10.16 14.75

% of Total Time 20.07% 25.96% 22.01% 31.96%

a All data from Day 2 were excluded from the analyses due to wiring harness being damaged during truck maintenance.

The compactor only and loader only opera tions when the PTO was ‘on’ were independently analyzed using a st atistical cluster analysis to he lp place the pressure observations into groups, or clusters, suggested by the data. Pressures in a gi ven cluster would tend to be similar to each other; thus, defining possible pressure modes. There ar e several varieties of clustering methods and the one chosen for this analysis was oriented toward finding disjoint clusters, i.e., clusters where the pressure valu es are placed in one and only one cluster. The disjoint cluster analysis wa s based on Euclidean distance computed from one or more quantitative variables. For the compactor only and loader only PTO “on’ operations, the only cluster variable was the pump pressure. Howe ver, for the situation where both the compactor and loader were operating simultaneously, both the compactor pump pressure and the loader pump pressure were used as th e two clustering variables.

The FASTCLUS ® procedure in the SAS ® software was used to perform all of the cluster analyses. This procedure divides the observations into clusters; i.e ., groups of data such that all Euclidean distances between observations in the same cluster are less than all Euclidean distances between observations in different clusters. The Euc lidean distances are computed using one or more quantitative variables. For ex ample, when both the compactor and loader of the tested refuse truck were operating simulta neously, both the compactor pump pressure and theFINAL REPORT 03-15777.14 20 of 38 loader pump pressure were used as the two clusteri ng variables. This kind of clustering is based

on a k -means model, and it uses a method called nearest cen troid sorting.

A typical cluster analysis cons isted of the following steps.

1. A first pass was made with FASTCLUS to find a set of points to use as the initial cluster seeds (i.e., a first guess of the means of the clusters). 2. Several independent FASTCLUS runs were th en made using 2, 3, 4, 5, 6, or 7 clusters with the saved seeds from Step 1. 3. For each run in Step 2, each observation wa s assigned to the nearest seed to form temporary clusters. The seeds were then repl aced by the means of the temporary clusters, and the process was repeated until no furt her changes occurred in the clusters. 4. For each computer run made in Step 2, the cubic clustering criterion (CCC) was computed. This criterion was used to dete rmine how many clusters were appropriate. When the CCC reached its maximum among th ese runs, the corresponding number of clusters being used provided a good estimate of the number of population clusters. For example, in the case described above for the refuse truck data with the two clustering variables, the chosen nu mber of clusters based on the CCC criterion was 4. 5. With the optimal number of clusters from Step 5, the FASTCLUS procedure was re-run specifying full replacement of the default seed us ed to form clusters. For our refuse truck example, there were 4 clusters. The output provided the number of observations in each of the 4 clusters and this was used to co mpute the proportion (weighting) for the duty cycle.

Histograms of the collected pump pressure da ta were individually examined for the compactor only and loader only data to assist in defining the possible number of clusters. Figure

_ 13 illustrates a relative freq uency histogram of the pump pressure during the compactor only PTO ‘on’ operation for the refuse truck. Note that the pressure data are skewed with the majority of the data concentrated around 250-280 psi with a small percentage of the

pressures

__ > 1000 psi. This possibly reflects the gr adual increase in compactor pressure throughout the day as the amount of garbage de posited in the truck increases causes the compactor to work harder to compress the contents . This characteristic is represented by Mode 4 of the compactor cycle.

Table 12 lists the cumulative percentiles of the compactor pump pr essure data for the refuse truck testing. Approximately 70% of the pump pressures lie below 374.58 psi while the 95 th percentile compactor pump pressure was at 765.38 psi.FINAL REPORT 03-15777.14 21 of 38 FIGURE 13. REFUSE TRUCK COMPAC TOR PRESSURE RELATIVE FREQUENCY HISTOGRAM FOR PTO “ON” OPERATION WHEN ONLY THE COMPACTOR WAS OPERATINGFINAL REPORT 03-15777.14 22 of 38 TABLE 12. COMPACTOR PRESS URE PERCENTILES FOR TIME WHEN ONLY THE COMPACTOR WAS IN OPERATION FOR REFUSE TRUCK TESTING

Percentile, % Pressure, psi 100 (max) 2624.63 95 765.38 90 633.89 80 471.13 70 374.58 60 328.60 50 295.50 40 265.15 30 234.81 20 202.63 10 173.20 5 161.25 0 (min) 150.21

A cluster analysis was performed on the co mpactor pressures with up to 5 possible clusters. The best analysis resulted in two clusters as defined in Table 13. Cluster #1 reflects the area identified in the histogram where the majori ty of the pressures are concentrated while cluster #2 represents the pressures in the long tail of the distribution. These two clusters were defined as the two steady-state modes for th e compactor-only PTO ‘on’ operation. The frequency counts of the two clusters were used to determine the relative proportion of time allocated to each steady-state mode. Finally, th e average pump pressure in each cluster was normalized as a percentage of the maximum opera ting pump pressure rating for the pump used in the refuse truck (2500 psi). Thus, the compact or-only PTO ‘on’ steady-state modes would be run at 11.24% of the rated maximum pump pre ssure for the compactor for Mode 1 and 29.28% for Mode 2.

TABLE 13. CLUSTER ANALYSIS RESULTS FOR COMPACTOR ONLY PTO “ON” OPERATION FOR REFUSE TRUCK

Cluster (Mode) Total Available PTO Test Time, sec % Time at Mode Avg Compactor Pressure, psi Min Compactor Pressure, psi Max Compactor Pressure, psi Normalized Avg. Pump

Pressure, % 1 17985 83.41 280.88 150.21 518.03 11.24 2 3576 16.59 732.03 518.94 2624.6 29.28FINAL REPORT 03-15777.14 23 of 38 Histograms of the collected pump pressure data were then examined for the loader only data to assist in defining the possible number of clusters. Figure 14 illustrates a relative frequency histogram of the pump pressure duri ng the loader only PTO ‘on’ operation for the refuse truck. Note that distribution of the pressu re data for this operation is very different than the one observed in the compactor only data. This distribution appears multi-modal reflecting the pressure changes during opera tion of picking up a container of garbage, dumping it in the truck and replacing the container on the group.

Table 14 lists the cumulative percentiles of th e loader pump pressure data for the refuse truck testing. Approximately 5% of the pump pressures ar e below 392.50 psi, 80% of the pressures lie below 1421.25 psi while the 95 th percentile loader pum p pressure was at 1845.00 psi.

FIGURE 14. REFUSE TRUCK LOADE R PRESSURE RELATIVE FREQUENCY HISTOGRAM FOR PTO “ON” OPERATION WHEN ONLY THE LOADER WAS OPERATINGFINAL REPORT 03-15777.14 24 of 38 TABLE 14. LOADER PRESSURE PERCENTILES FOR TIME WHEN ONLY LOADER WAS IN OPERATION FOR REFUSE TRUCK TESTING

Percentile, % Pressure, psi 100 (max) 2130.00 95 1845.00 90 1782.50 80 1421.25 70 1359.63 60 1295.25 50 1204.26 40 1113.25 30 1031.43 20 926.63 10 714.26 5 392.50 0 (min) 150.71

A cluster analysis was performe d on the loader pressures with up to 5 possible clusters. The best analysis result ed in four clusters as defined in Table 15. Cluster #1 reflects the area identified in the histogram where the pressure s are the lowest and starting to increase in frequency after 500 psi. Cluster #2 represents the pr essures increasing up through approximately 1150 psi while Cluster #3 includes the highest number of data points at slight ly higher pressures. Lastly, Cluster #4 is shown in the histogram as the single be ll-shaped distribution with the highest pressure values. These four clusters were defined as th e four steady-state modes for the loader-only PTO ‘on’ operation. The frequency counts of the four clusters were used to determine the relative proportion of time allocated to each steady-state mode. Finally, the average pump pressure in each cluster was normalized as a percentage of the maximum operating pump pressure rating for the pump used in the refuse truck (2500 psi). Thus, the loader-only PTO ‘on’ steady-st ate modes would be run at 12.87% of the rated maximum pump pressure for the loader for Mode 1, 38.26% of rated pressure for Mode 2, 52.84% of rated pressure for Mode 3, and 72.99% for Mode 4.FINAL REPORT 03-15777.14 25 of 38 TABLE 15. CLUSTER ANALYSIS RESULTS FOR LOADER ONLY PTO “ON” OPERATION FOR REFUSE TRUCK

Cluster (Mode) Total Available PTO Test Time, sec % Time at Mode Avg. Loader Pressure, psi Min Loader Pressure, psi Max Loader Pressure, psi Normalized Avg. Pump

Pressure, % 1 1310 7.17 321.65 150.71 603.03 12.87 2 6698 36.64 956.50 603.94 1147.26 38.26 3 7694 42.08 1320.95 1148.18 1614.25 52.84 4 2581 14.12 1824.74 1616.13 2130.00 72.99

The last analyses consisted of examining pressure data when both the compactor and loader were operating at the same time. Histogr ams of the collected pump pressure data were examined for the compactor and loader data to a ssist in defining the possi ble number of clusters for the simultaneous operation. Figure 15 illustra tes a relative frequency histogram of the compactor pump pressure during the simultaneous PTO ‘on’ operation for the refuse truck. Note that the distribution of the pressure data for th is operation was very similar to the one found in when the compactor was used alone. Figure 16 de picts the distribution of loader pump pressures during the simultaneous operation with the compact or. Again this looks very similar to the operation of the loader only pump pressure data. This may confirm that the two hydraulic loops operate independently regardless of whether they are working alone or in combination with one another. Table 16 lists the cumulative percentil es of the loader pump pressure data and the compactor pump pressure data for the refuse tr uck during simultaneous operation. Note that these percentiles are very closely related to th e individual pump pressure s for the compactor and loader found in Table 12 and Table 14, respectiv ely. Lastly, Table 17 is a two way frequency table of the percent of total time spent at various combinations of pressure intervals for the compactor and the loader. Note that approximate ly 78% of the pressure data were collected when the compactor pressure was ≤ 350 psi.FINAL REPORT 03-15777.14 26 of 38 FIGURE 15. REFUSE TRUCK COMPAC TOR PRESSURE RELATIVE FREQUENCY HISTOGRAM FOR PTO “ON” OPERAT ION WHEN BOTH COMPACTOR AND LOADER WERE OPERATING

FIGURE 16. REFUSE TRUCK LOADE R PRESSURE RELATIVE FREQUENCY HISTOGRAM FOR PTO “ON” OPE RATION WHEN BOTH COMPACTOR AND LOADER WERE OPERATINGFINAL REPORT 03-15777.14 27 of 38 TABLE 16. COMPACTOR AND LOADER PRESSURE PERCENTILES FOR TIME WHEN BOTH WERE IN OPERATIO N FOR REFUSE TRUCK TESTING

Compactor Loader Percentile, % Pressure, psi Percentile, % Pressure, psi 100 (max) 2155.75 100 (max) 2146.63 95 651.35 95 1854.25 90 455.50 90 1788.00 80 358.03 80 1428.63 70 327.68 70 1367.88 60 306.54 60 1283.38 50 285.39 50 1173.00 40 264.24 40 1075.55 30 238.49 30 991.90 20 208.14 20 865.95 10 173.20 10 573.60 5 160.33 5 214.15 0 (min) 150.21 0 (min) 150.71

TABLE 17. PERCENT OF TOTAL TIME AT COMPACTOR AND LOADER

PRESSURE WHEN BOTH ARE OPE RATING FOR THE REFUSE TRUCK

Compactor pressure, psi Loader Pressure, psi

150- 350 350.1- 550 550.1- 750 750.1- 950 950.1- 1150 1150.1- 1350 1350.1- 1550 1550.1- 1750 1750.1- 1950 >1950 Total

150-250 2.18 0.79 1.69 3.85 7.35 7. 09 6.20 0.79 3.84 0.35 34.12

250.1-350 2.24 0.90 1.76 4.99 10.77 8.10 8.95 0.75 4.72 0.69 43.87

350.1-450 1.09 0.35 0.49 1.03 2.23 2.74 2.50 0.18 1.03 0.14 11.78

450.1-550 0.53 0.05 0.14 0.41 0.58 0.50 0.39 0.06 0.28 0.02 2.96

550.1-650 0.71 0.04 0.07 0.25 0.32 0.37 0.24 0.04 0.17 0.01 2.22

650.1-750 0.52 0.01 0.07 0.16 0.28 0.16 0.14 0.03 0.08 0.02 1.46

750.1-850 0.11 0.01 0.06 0.20 0.16 0.11 0.13 0.02 0.08 0.00 0.89

850.1-950 0.04 0.02 0.02 0.11 0.13 0.14 0.09 0.02 0.06 0.00 0.64

950.1-1050 0.02 0.01 0.03 0.11 0.08 0.07 0.05 0.02 0.05 0.00 0.44

>1050 0.08 0.04 0.05 0.33 0.40 0. 25 0.19 0.09 0.16 0.01 1.61

Total 7.54 2.24 4.37 11.44 22.28 19.55 18.88 1.99 10.47 1.24 100FINAL REPORT 03-15777.14 28 of 38 The final cluster analysis was performed us ing the compactor and loader pressures as cluster variables when both of these component s were operating simultaneously. Analyses with up to 5 possible clusters were performed. Th ese cluster analyses did not produce good results when all the data were used. Upon examinati on of a scatterplot of compactor and loader pressures it appeared that perhaps the very high le vels of compactor pressu res that were sparsely populated along the loader pr essure range may have had an infl uence in identifying the clusters due to their very large distances from a cluste r mean. Therefore, as an attempt to obtain adequate cluster definitions, onl y the compactor data <550 psi were used (this was approximately 93% of the entire compactor and loader pressure data ). This analysis resulted in four clusters as illustrated in Figure 17 and define d in Table 18. In Figure 17, th e black dots represent the four cluster mean pressures while the four different colored ‘+’ symbols represent the compactor and loader pressures within an identified cluster. As can be seen in Table 18 the average compactor pressure for all four clusters is very close and that the loader pressures were more dominant in minimizing the distances of the pr essures from the cluster average pressure. Also, the average loader pressures for the four clusters were very similar to the average pressures in the four clusters in the analysis of the loader only data . Upon consultation with EPA, it was decided to define four clusters with the same range of load er pressures as was identified in the loader only analysis and to compute the loader average for the four clusters using all the data collected when both the loader and compactor were in operation. It was also decided to compute the average compactor pressure over all the data collected when both the loader and compactor were in operation and to assign the compactor pressure aver age to all four clusters. The resulting steadystate modes for the simultaneou s operation of the compactor a nd loader are listed in Table

_ 19. Finally, the average compactor and loader pump pressure in each cluster was normalized as a percentage of the maximum operatin g pump pressure rating for the pump used in the refuse truck (2500 psi). Thus, the simultaneous operation of th e compactor and loader PTO ‘on’ steady-state modes would be run at 12.81% of the rated maxi mum pump pressure for the compactor for all four modes. The loader would be run at 11.08% of the rated maximum pump pressure for Mode 1, 38.18% for Mode 2, 53.42% for Mode 3, and 73.54% for Mode 4.FINAL REPORT 03-15777.14 29 of 38 FIGURE 17. CLUSTER ANALYSIS MEANS FOR REFUSE TRUCK WHEN BOTH LOADER AND CO MPACTOR WERE OPERATING USING SELECTED DATA

TABLE 18. CLUSTER ANALYSIS RESULTS FOR BOTH COMPACTOR AND LOADER PTO “ON” OPE RATION FOR REFUSE TRUCK USING SELECTED DATA

Cluster Avg. Compactor Pump Pressure, psi Avg. Loader Pump Pressure, psi Approx Loader Pressure Range, psi 1 292.574 279.954 150-560 2 275.697 940.789 561-1160 3 279.927 1323.218 1161-1560 4 271.900 1837.271 >1560FINAL REPORT 03-15777.14 30 of 38 TABLE 19. FINAL STEADY-STA TE MODES FOR BOTH COMPACTOR AND LOADER PTO “ON” OPE RATIONS FOR THE REFUSE TRUCK USING ALL DATA

Mode % Time

at Mode Avg. Compactor Pump Pressure, psi Avg. Loader Pump Pressure, psi Max Compactor and Loader Pump Pressure, psi Normalized Avg. Compactor Pump Pressure, % Normalized Avg. Loader Pump Pressure, % 1 10.31 320.33 277.03 2500 12.81 11.08 2 37.42 320.33 954.05 2500 12.81 38.16 3 39.00 320.33 1335.61 2500 12.81 53.42 4 13.27 320.33 1838.38 2500 12.81 73.54FINAL REPORT 03-15777.14 31 of 38 5.0 TASK 4 - DUTY CYCLE DEVELOPMENT

This task involved the development of a co mposite duty cycle for EPA PTO testing using both the duty cycle information from the utility boom truck and the ASL refuse truck as defined in Task 3. Upon EPA recommendation, the duration of the composite cycle was targeted to be approximately 10 minutes. Data and information collected in Task 1 were used in weighting different portions of the composite duty cycle in order to reflect actual field PTO operations in the population according to usage of utility truck for ASL refuse truck. Table 20 identifies the amount of time each vehicle type and applicati on would be included in a 10-minute composite duty cycle.

TABLE 20. COMPOSITE 10- MINUTE CYCLE TIMES BY VEHICLE AND APPLICATION

Vehicle Population Weighting % Application Application Weighting % Composite Cycle Weighting % Composite Cycle Time (min) Composite Cycle Time (sec) Utility Truck 60 Rural 20 12 1.2 72 Urban 80 48 4.8 288 Refuse Truck 40 Residential 100 40 4.0 240

The weightings and composite cycle time for eac h vehicle application were applied to the information for each vehicle mode identified in Ta sk 3 from the usage data analyses. Table 21 lists the amount of actual time allotted to each of these vehicle modes assuming a 10-minute composite duty cycle. The next step was to deci de if the times allotted to each mode by vehicle application were to be applied entirely during one testing sequence or if they were to be divided into repetitive ‘cycles’. Fo r the utility truck application, its operation warranted a single continuous test time for each mode as it reflecte d how the utility operation functions. But the idle times associated with the rural and urban usag e were divided in half so that the utility truck operations started and en ded with idle time.

Conversely, the refuse truck loader and co mpactor operations did represent usage that was cyclic in nature. The loader cycle characterized the picking up of the refuse receptacle, raising it to the truck, emptying the contents and replacing it to the ground. This process was repeated throughout the day as the refuse truck performed its duties. Therefore, a discrete Fourier transform using the fast Fourier transf orm (FFT) algorithm was performed on the loader and compactor data independently. The results of the FFT from the compactor data are shown in Figure 18. It can be seen that there is more than one frequency present. For this test cycle, 0.025 Hz was chosen due the high strength and ma tching closely to what was observed visually in the raw data files. The FFT results for the loader, Figure 19, ar e less clear. There is not a distinct peak, but the highest st rength varies from 0.01 Hz to 0.03 Hz. The total time for the compactor –only operation, with idle, was calcul ated to be 74 seconds. The period of the compactor cycle was 40 seconds, so it was deci ded to divide the compactor operation by two instead of increasing the cycle time to 80 seconds. For simplicity and lack of better evidence, it was decided to use two ‘cycles’ for loader onl y, compactor only, and both loader and compactorFINAL REPORT 03-15777.14 32 of 38 modes in order to comply with the total test tim es associated with the modes identified for the refuse truck. More cycles c ould be added but the resulting co mposite duty cycle time would also increase.

FIGURE 18. FFT PLOT FOR REFU SE TRUCK COMPACTOR OPERATION

FIGURE 19. FFT PLOT FOR RE FUSE TRUCK LOADER OPERATION 0 0.01 0.02 0.03 0.04 0.05 0.06 0 2 4 6 8 10 12 x 10 -3

Compactor Frequency, HzStrength

0 0.01 0.02 0.03 0.04 0.05 0 0.005

0.01 0.015

0.02 0.025

0.03 0.035

0.04

Loader Frequency, HzStrengthFINAL REPORT 03-15777.14 33 of 38 TABLE 21. COMPOSITE 10-MINUTE CYCLE TIMES FOR EACH MODE

Vehicle Application Mode % Time at Mode Composite Cycle Time (sec) Computed Time at Mode, sec Actual Time at Mode, sec

Utility Rural 1 9.66 72 6.96 7 2 (Idle) 90.34 72 65.04 65

Urban 1 49.89 288 143.68 144 2 (Idle) 50.11 288 144.32 144

Refuse Loader Only 1 7.17 240 3.78 4 2 36.64 240 19.35 20 3 42.08 240 22.23 22 4 14.12 240 7.46 8 5 (Idle) 10.65 240 25.57 26
Compactor Only 1 83.41 240 51.97 52 2 16.59 240 10.33 10 3 (Idle) 10.65 240 25.57 26

Both Loader and Compactor 1 10.31 240 4.97 4 2 37.42 240 18.03 18 3 39.00 240 18.78 18 4 13.27 240 6.39 6 5 (Idle) 10.65 240 25.57 26 Total Time, sec 600

Table 22 lists the proposed 10-minute composite duty cycle for the PTO operation based on the analysis of the data collected on the utility truck and ASL refuse truck.FINAL REPORT 03-15777.14 34 of 38 TABLE 22. FINAL COMPOSIT E 10-MINUTE PTO DUTY CYCLE

Time,

sec Utility Truck or Refuse Compactor

Pump 1 Refuse Loader Pump 2 Vehicle Application Mode Time (sec) 0-32 0 0 Utility Rural 2 (Idle) 32 (1/2 of total idle time) 33-39 80.45 0 Utility Rural 1 7 40-72 0 0 Utility Rural 2 (Idle) 33 (1/2 of total idle time) 73-144 0 0 Utility Urban 2 (Idle) 72 (1/2 of total idle time) 145-288 83.47 0 Utility Urban 1 144 289-360 0 0 Utility Urban 2 (Idle) 72 (1/2 of total idle time) 361-362 0 13 Refuse Loader 1 2 363-372 0 38 Refuse Loader 2 10 373-383 0 53 Refuse Loader 3 11 384-387 0 72.99 Refuse Loader 4 4 388-400 0 0 Refuse Loader 5 (idle) 13 401-402 0 13 Refuse Loader 1 2 403-412 0 38 Refuse Loader 2 10 413-423 0 53 Refuse Loader 3 11 424-427 0 72.99 Refuse Loader 4 4 428-440 0 0 Refuse Loader 5 (idle) 13 441-466 11.24 0 Refuse Compactor 1 26 467-471 29.28 0 Refuse Compactor 2 5 472-484 0 0 Refuse Compactor 3 (idle) 13 485-510 11.24 0 Refuse Compactor 1 26 511-515 29.28 0 Refuse Compactor 2 5 516-528 0 0 Refuse Compactor 3 (idle) 13

529-530 12.81 11.08 Refuse Compactor and Loader 1 2

531-539 12.81 38.162 Refuse Compactor and Loader 2 9

540-548 12.81 53.42 Refuse Compactor and Loader 3 9

549-551 12.81 73.53 Refuse Compactor and Loader 4 3

552-564 0 0 Refuse Compactor and Loader 5 (idle) 13

565-566 12.81 11.08 Refuse Compactor and Loader 1 2

567-575 12.81 38.162 Refuse Compactor and Loader 2 9

576-584 12.81 53.42 Refuse Compactor and Loader 3 9

585-587 12.81 73.53 Refuse Compactor and Loader 4 3

588-600 0 0 Refuse Compactor and Loader 5 (idle) 13FINAL REPORT 03-15777.14 35 of 38 6.0 TASK 5 - TEST RIG RE SEARCH AND DEVELOPMENT

A hydraulic system simulator has been desi gned, but not built or tested, that may enable the simulation of the hydraulic load on the pumps of a refuse hauler while conducting chassis dyno testing of the vehicle. The simula tor circuit schematic, shown in Figure 20, consists of two parallel circuits so that an individual lo ad can be applied to each pump of a tandem pump system.

FIGURE 20. HYDRAULIC SYSTEM SIMULATOR CIRCUIT SCHEMATIC 

## From Vehicle Pump #1 From Vehicle Pump #2

Return to Vehicle Hydraulic Reservoir FM 1 FM 2 P1 P2

PC1 PC2

BV1 BV2FINAL REPORT 03-15777.14 36 of 38 The outlet port for each pump must be disconne cted from the system and attached to each line going to the hydraulic system simulator. The disconnected pump outlet lines must be capped off. The return line from all the system control valves to the sy stem hydraulic reservoir must also be intercepted, before the system hydr aulic cooling system and before any return line filtration. This line can be intercepted by “T’ing” into the return line. The return line from the system simulator should be attached to this “T”. Alternatively, instead of a “T”, the return from the system control valves can be disconnected and capped and the hydraulic simulator can be connected to the return system on the vehicle.

The operation of each leg of the circuit, show n in Figure 20, is identical. The following discussion will be for the circuit for Pump #1, but applies similarly to the circuit for Pump #2. During normal no-load operation, to simulate when the hydraulic system is in Neutral, none of the valves are activated and flow from the Pump #1 passes through the Bypass Valve, BV1, and then returns back to the vehicle with very little backpressure on the pump. The Bypass Valve is a normally open, solenoid operated valve, so in this condition, it should not be activated. The flow rate from Pump #1 is measured by the Flow Me ter, FM 1, and the pressure on the pump is measured by the Pressure Transducer, P 1.

The hydraulic system simulator simulates a load by diverting the pump flow through a proportional electro-hydraulic relief valve. The el ectronic control signal is first applied to the Pressure Control valve, PC 1, and then the B ypass Valve should be activated. The Pressure Control valve regulates the pressure in the line from the pump in proportion to the electronic control signal. Prior to testing, the Pressure Co ntrol valve should be calib rated to determine the proper control signal at a given flow rate that w ill result in the desired pressure the needs to be simulated. Better control accuracy can be obt ained by employing a closed loop control on
pressure.

Hydraulic valves for the simu lator have been selected. The supplier is Sun Hydraulics and a list of the required valves is below:

Description Part No. Quantity
2

‐ Way, Poppet Directional Valve with in

‐ line body DFEA

‐ 8DN

‐ IEN 2
2

‐ Way, Solenoid Operated Directional Spool

‐ Pilot, w/ 12V Coil DAA

‐ MHN

‐ 712 2 Pilot Operated, balanced piston relief main stage with in

‐ line body RPIC

‐ 8WN

‐ IEN 2 Electro

‐ proportional relief valve

‐ Pilot with imbedded amplifier RBAP

‐ XAN

‐ 4A12V 2 Hand Held Programmer 991

‐ 700 1 Cable for Programmer 991

‐ 702 1

These valves are screw in type cartridge valves. They require a body, or manifold to screw into. Line mounted bodies ar e included in the part number fo r the respective valves. These valves would then need to be plumbed together with appropriate fittings to create the circuit shown in Figure 21. An alternate approach would be to have a custom manifold fabricated that would duplicate the circu it shown in the box in Figure 20. This manifold would be much more compact and simple.FINAL REPORT 03-15777.14 37 of 38 The proportional pressure control valve includes an integral digital amplifier. It requires a hand held programmer to configure the amplifier. The amplifier converts a low level analog signal to a higher power current to power the proportional solenoid.FINAL REPORT 03-15777.14 38 of 38 7.0 SUMMARY

The Environmental Protection Agency (EPA) requested Southwest Research Institute (SwRI) to evaluate engine and vehicle performan ce of utility vehicles and refuse haulers for boom operation. SwRI performed a literature sear ch and interviewed various industry contacts to determine which vehicles’ PTO systems might be hybridized in signif icant quantities in 2011 and beyond. SwRI determined that there were cu rrently only two types of vehicles meeting those requirements, utility boom trucks and automated side loader (ASL) refuse haulers.

SwRI obtained permission to instrument a utility boom truck in two different locations, urban and rural, and an ASL refuse truck opera ting in a suburban area. A data acquisition system was installed on each truck to record data from transducers measuring PTO hydraulic pressure and flow and engine sp eed, engine load, engine fuel ra te, and vehicle speed from the vehicle’s J1939 network.

In-field hydraulic pressure data were collec ted over a period of se veral days using two application-specific vehicles: utility and refuse trucks. Definitions of power take-off (PTO) operations were identified as (1) pump “on” and idle (utility truck), and (2) compactor only, loader only, both compactor and loader, and idle (refuse truck). Steady-state pressure modes were identified by a statistical disjoint cluster an alysis. Statistical frequency analyses of the infield data were used to determine the relative proportion of time allocated to each steady-state mode. Information collected on population usage wa s used to weight different portions of the composite duty cycle (utility and refuse truck cycles) to reflect actual field PTO operations.

A test rig was designed to test vehicle PTO systems according to the test cycle’s specifications. The design uses off-the-shelf part s and includes two test ci rcuits to accommodate vehicles equipped with two indepe ndent hydraulic circuits. The system has not been built or tested, but principle of operation should allow others with hydraulic system experience build a system to meet the test cycle specifications.