Simulating Operability
of Wheel Loaders
Dr. Reno Filla
Volvo Construction Equipment
Emerging Technologies
Making working machines
more energy-efficient
and easier to operate
...by:
1. understanding the machine as one system
2. understanding the interaction between
machine, operator and working environment
Business idea for the OEM
Find perfect balance
Design machines with a natural,
workload-minimising way to operate
with
• productivity as high as required
• energy efficiency as high as possible
Give assistance to the operator if needed
(guidance).
Focus: Conceptual Design phase
Product Development
Concept design
Concept evaluation
Productivity
Energy efficiency
Operability
Concept evaluation
Productivity
Energy efficiency
Operability
Early days of simulation:
We were lacking the operator
and the working environment
Operator model
Discrete-event approach (finite state machine)
This image cannot currently be displayed.
Rules gained
in interviews
Rules gained
in interviews
Operator model
Discrete-event approach (finite state machine)
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
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Extension from V- to Y-cycle
Operator model
Discrete-event approach (finite state machine)
Rules gained
in interviews
Some rules for bucket filling:
•
•
•
•
•
Accelerate to certain initial velocity
Shift to 1st gear when bucket in gravel
Lift somewhat
Keep advancing
When wheel about to slip:
less gas pedal value and start lifting
• When lift pressure > max: tilt backward
Operator model
Discrete-event approach (finite state machine)
Rules gained
in interviews

Operator model
Discrete-event approach (finite state machine)
Rules gained
in interviews
Operator model
Discrete-event approach (finite state machine)
Operator model
useful for simulation of
• Productivity and
• Energy efficiency (fuel consumption)
Operator workload study
18 operators with varying skill (from inexperienced to expert)
performed bucket loading with a wheel loader
• 3 settings where traction force was limited via software
• …which has a heavy impact on ease of bucket filling
with following data acquired
• data from CAN bus and external sensors
• video
• self-evaluations on machine and own performance
Operator workload study
Hypothesis:
• The control commands of the operator (control effort)
are indicative of the machine’s operability (in bucket loading)
• Higher use of operator controls indicates higher workload
and thus lower operability
Human operator’s
use of machine
controls
Human operator’s
perception of
machine’s operability
Operator model’s
use of machine
controls
Operator workload study
Hypothesis:
• The control commands of the operator (control effort)
are indicative of the machine’s operability (in bucket loading)
• Higher use of operator controls indicates higher workload
and thus lower operability
lift lever
Result:
• Hypothesis confirmed
• Algorithms developed
tilt lever
between control commands
and ease of bucket fill
22
27
26
In support of the hypothesis
Strictly monotone relationship
28
29
12
Monotone relationship
14
25
20
08
06
Operator skill
0
25
50
04
Neutral (constant)
None-monotone
relationship
Inverse relationship
75
100
11
13
21
02
18
05
Load-normalized Control effort with “Split & Merge” algorithm, arithmetic sum
Product Development
Concept design
Concept evaluation
Operator models
Control effort measure
Productivity
Energy efficiency
Operability
Product Development
Concept design
Thank you!
Ideas, comments or questions?
[email protected]