Haul Cycle Analysis

This command is used for detailed analysis of haul routes using various haul trucks to determine either 1) the required truck fleet required to meet a target production or 2) the attainable production based on a given haul fleet. This command requires the user to have executed the Haul Road Manager to define the haulage route. Although optional, it is recommended to define and customize truck parameters using the Haul Fleet Manager command to ensure the most accurate results. The first section of this document discusses the basic use of this routine, while the second section discusses the actual calculations that are performed to analyze the haul cycle.

Basic Use

First, you will be prompted to select the start and ending points of the haul road to be considered. The dialog that appears will show a spreadsheet view of all potential routes between the starting and ending point which will be sorted by distance in increasing order. The dialog will change slightly depending on the ‘Calculate’ option selected (either Fleet Size or Production).



Reports

The Haul Cycle Analysis command is very quick and dynamic. Whenever a value is edited, the results in the spread sheet view will be automatically updated. These results can be reported in a variety of formats as discussed below.
CAT FPC Reports: This option will allow you to export one of three report types: ASCII, GPS, and Course.

The ASCII report will export the segment distance, the rolling resistance, the slope, and the speed of the truck along each segment into an .asc file as shown below:

The GPS report will export the coordinates and elevation of the haul road at each vertex representing the road. This report can be saved as an Excel spreadsheet (.xls file) as shown below:

The Course Report is reported in a spreadsheet with three tabs: General Info, Haul, and Return. This file can also be saved as an Excel spreadsheet, as shown below:

Cycle Report: This report gives basic information about the haul cycle.

Cycle Detail Report: This report provides more detailed information about the haul cycle, which in addition to the information in the standard report, provides information about the transition of speed along each segment, the rimpull applied on each road, and detailed information about the sub-segments which are used in the calculations.

Create Flyby Log: This option will create a .pos file which can be reviewed with the Surface 3D Flyover command in the Civil module. You will be prompted to enter a road width, then you will be allowed to specify the file name.

Process Spoil Timing: This command will perform a timing analysis on an exported .sph file from Spoil Placement Timing. This will give a more detailed analysis of the haul cycle during each time period of the spoil placement. An example report is provided below:

Calculation Methods

A good planner will be cautious about blindly accepting calculations. For this reason, the following section details the logic and calculations used in Haul Cycle Analysis so that the user can fully understand how the routine works.

As previously stated, this routine seeks to calculate either the attainable production based on the truck fleet or the fleet size required to meet a target production. Actually determining these values is rather simple once to the true cycle time has been calculated. However, calculation of the cycle time considers many factors. The first sub-section of this section details how the program calculates cycle time. The following sub-section details how the attainable production and required fleet size are calculated based on the calculated cycle time.

Calculation of Cycle Time

The diagram shown below is visual outline of the equations used to calculate the haul cycle time. This is provided to allow for a better understanding of how Haul Cycle Analysis uses input variables to determine various operating parameters. Note that this diagram is simplified, and does not detail all of the logic used in the actual routine.

The total haul cycle time can be calculated with the following equation:
where

Three variables, TLoad, TDump, and TQueue, are manually entered. The remaining variables, TTravel-loaded and TTravel-empty, are calculated similarly to one another, but with different values based on the road profile and truck specifications for loaded and empty scenarios. TTravel-loaded and TTravel-empty are calculated with the following formula:
TTravel-(loaded or empty)=TSegment-1+TSegment-2+⋯TSegment-n
where
    TSegment-1 is the travel time of the first segment of the haul route
    TSegment-2 is the travel time of the second segment of the haul route
    Etc.

The travel time for a single haul segment will be further divided into three sub-segments according to the following chart.
    Sub-segment #1: the truck is accelerating/decelerating at a constant rate
    Sub-segment #2: the truck is traveling at a constant velocity
    Sub-segment #3: the truck is braking. Note that sub-segment #3 is only used when the truck comes to a complete stop.

In the below picture:
  1.     Sub-segment #1 shows the truck accelerating as it travels uphill to meet the new road speed limit
  2.     Sub-segment #2 shows the truck traveling at a constant velocity once it reaches the road speed limit
  1.     Sub-segment #1 shows the truck decelerating as it starts to travel downhill to meet the new road speed limit
  2.     Sub-segment #2 shows the truck traveling at a constant velocity once it reaches the road speed limit
  1.     Sub-segment #2 shows the truck traveling at a constant velocity. It is traveling at the speed limit when it approaches Haul Segment 3.
  2.     Sub-segment #3 shows the truck braking as the truck comes to a complete stop.

The total travel time for a haul segment is simply a sum of the sub-segment travel times, as shown below:
TSegment=(TSub-segment-1+TSub-segment-2+TSub-Segment-3)
The travel time of each sub-segment is calculated using the following formulae:


where

Sub-Segment #1 Supplement

Vmax-allowable is minimum of:
amax-allowable is minimum of:

Note that a truck’s velocity does not necessarily have to increase during sub-segment #1. If a truck enters a haul segment at a speed which exceeds the maximum allowable velocity for the haul segment, then sub-segment #1 will refer to a decelerating situation.

Sub-Segment #2 Supplement

In the final report, sub-segment distances will be reported as D1, D2, and D3, which refer to the distances of the respective sub-segments. The distance for each sub-segment is calculated as shown below. Here it is also important to note that the sub-segment #3 is further divided into three sections which represent A) the time required for the driver to realize that a stop is required, B) the time from when the driver first applies the brake to the time when the brake system applies the full braking force, and C) the time required for the truck to stop once the full braking force is applied.

Note that in many situations one or two of these sub-segments will not be used in the final calculations. For example, if a truck enters a new haul segment and does not need to accelerate/decelerate to meet the speed limit, the distance and travel time for sub-segments #1 and #3 will be zero. As another example, sub-segment #3 will only be used when the truck is braking to a complete stop.

where

Sub-segment #3 Supplement

dmax-allowable is minimum of:

Note that the program will iteratively check for the distance required for the truck to come to a complete stop without exceeding the maximum deceleration rate.

Max Truck Acceleration/Deceleration

Both sub-segments #1 and #3 must check for the maximum allowable acceleration/deceleration rate, and one of the rates to be considered is the rate limited by friction, also referred to as the useable rimpull. The below equations show how the acceleration/deceleration rates are calculated.

As previously shown, Haul Cycle Analysis analyzes truck movement by constant acceleration/deceleration along sub-segments and sections of sub-segments. For this reason, the acceleration of the truck can be defined by scalar quantities in Newton’s Second Law of motion, shown below and simplified:

where
    F is the sum of all forces acting on the truck
    M is the mass of the truck
    amax-attainable is the maximum possible acceleration of the truck
    FRimpull is the effective rimpull force (minimum of available rimpull and useable rimpull force)
    FRolling is the force of rolling resistance, which is set within the Haul Road Manager for each haul segment
    FGrade is the grade resistance force, defined as positive for uphill and negative for downhill movement

FRimpull



Available Rimpull is determined from standard Rimpull Curves provided by truck manufacturers. This data is entered into the Haul Fleet Manager in a tabular format in the Rimpull Table. From the entered values, the program will determine the available rimpull at various operating speeds.

Useable rimpull is the maximum force the truck can apply before the tires start to slip on the road. This value is calculated with the following equation


where

Furthermore, D can be calculated with the following equation

where
    RAWDLoad – drive (rear) axle weight distribution percentage in loaded condition, expressed as a decimal
    RAWDEmpty – drive (rear) axle weight distribution percentage in empty condition, expressed as a decimal
    NPL – nominal payload
    GVW – gross vehicle weight; note that will not always equal the loaded truck weight

FRolling


Where
Cr is the haul segment rolling resistance, expressed as a decimal; this is set in the Haul Road Manager

FGrade


Although this calculation does not perfectly calculate the resistive/assistive force due to the grade of the road, the difference between the calculated value and the ‘true’ value is considered insignificant. Once the maximum possible acceleration of the truck has been calculated, this value is compared to the maximum acceleration limit set in the Haul Fleet Manager. The minimum of these two values is used for the calculation of the distance and travel time of sub-segment #1 for each haul segment.

Maximum Deceleration

When a truck slows down, it is limited to using the lesser of two possible deceleration rates. One rate is defined directly in the Haul Fleet Manager. The other rate is calculated based on Newton’s Second Law using the below formulae:

where


Calculation of Required Fleet Size and Attainable Production

Once the total cycle time has been calculated, the calculation of the required fleet size/attainable production is very simple. The calculations for these values are shown below

Where

Note that the total attainable production is the sum of each attainable production rate of each truck in the haul fleet.

References:

Parreira, Julianna. "An Interactive Simulation Model to Compare an Autonomous Haulage Truck System with a Manually-Operated System." Diss. THE UNIVERSITY OF BRITISH COLUMBIA (VANCOUVER), 2013. Print.

U.S. Department of Labor. MSHA Haul Road Inspection Handbook. June 1999. Handbook Number PH99-I-4.

Prompts

Delay: Intersection Merge (will be a pre-named delay name)
[near on] Pick start point on Haul Road: select where the truck will begin, usually where it gets loaded at.
[near on] Pick end point on Haul Road: select where the truck will end, usually where it unloads/dumps at.

Pull-Down Menu Location: Reserves/Timing in Surface Mining
Keyboard Command: haul_cycle