Article
citation information:
Wheatley, G., Popoola, S. Autonomous transmission
control of a 2017 Yamaha Grizzly 700 all-terrain vehicle. Scientific Journal of Silesian University of Technology. Series
Transport. 2021, 110, 183-198.
ISSN: 0209-3324. DOI: https://doi.org/10.20858/sjsutst.2021.110.15.
Greg WHEATLEY[1],
Samuel POPOOLA[2]
AUTONOMOUS
TRANSMISSION CONTROL OF A 2017 YAMAHA GRIZZLY 700 ALL-TERRAIN VEHICLE
Summary. Investigation on a
designed and modified standard automatic transmission for a 2017 Yamaha Grizzly
All-Terrain Vehicle was carried out to allow it to be controlled remotely and
autonomously while maintaining its ability to be manually operated. The vehicle
is a part of a project named AutoWeed. This project aims at developing a
vehicle which can be used in the Australian outback to control and eradicate
weeds. Preliminary tests were conducted on the vehicle to determine the
performance parameters required to replace the movement supplied by the
operator. Several devices used to achieve this motion were explored. It was
concluded that the Motion Dynamics HB-DJ806 - LALI10010 electromechanical
linear actuator be used as a proof of concept device for this application. This
device is capable of exerting 200 N at 35 mm/seconds. It has a stroke length of
50 mm and was powered by a 12V DC motor, which drew 3 amps at maximum load.
Through testing, it was found that the selected actuator did not have enough
stroke length to cycle through the five gears on the ATV. This error was
rectified allowing the system to function as intended. To achieve a
reliable design, however, the Linak LA14 actuator was purchased as a final
design as it was stronger, faster and had feedback capabilities. Before
procurement, the new actuator was digitally modelled using SolidWorks 2017 and
3D printed to confirm the mounting position and method. An ANSYS FEA was
conducted on all the custom-made components including the actuator bracket and
mounting plate to ensure reliability. The bracket model was manufactured using
3D printing from ABS. It was recommended that for reliability, the bracket
should be constructed from a stronger material such as aluminium. The results
gained from testing proved that the autonomous transmission system implemented
was reliable and repeatable. This was justified as the system achieved a 100%
success rate when cycling through gears.
Keywords: autonomous, ANSYS, Finite Element Analysis,
transmission
1.
INTRODUCTION
Australia’s
agricultural industry is worth over 100 million AU dollars and is one of the
world’s largest industries [2, 6]. For centuries, the agricultural
industry operated on human power alone, eventually evolving to the utilisation
of animals such as horses and donkeys to simplify tasks. For approximately 100
years, the use of tractors dominated the industry. Although larger autonomous
vehicles are being developed, there has been very little advancement in the
atomisation of smaller vehicles such as all-terrain vehicles (ATV). Honda, the
University of Bath, North Carolinas Urban Research University and Harper Adams
University, are all institutions, which have developed early design prototypes
proving the possibility of manufacturing a fully autonomous and
remote-controlled ATV. However, there is no vehicle of this type that is fully
developed, functional or commercially available. A fully autonomous all-terrain
vehicle would appeal to farmers who want to improve productivity, profitability
and reduce the required man time to perform tedious tasks such as spraying
weeds.
A team (Auto
Weed) at James Cook University have worked on designing an autonomous robotic
weed control vehicle. This was performed by converting a 2017 Yamaha Grizzly
700 from its current standard manual operable controls to a fully autonomous
system, pictured in Fig. 1.
Fig. 1. 2017
Yamaha Grizzly [26]
The 2017
Yamaha Grizzly 700 associated with this investigation has an automatic 5-gear
position gearbox. This design problem requires the determination of a solution
to achieve specific gear selection without human interaction.
Weed control
has been an interest to farmers according to available literature, since before
1200 A.D [23]. The task of eradicating or controlling the growth and spread of
weeds is crucial to farmers due to the need to maintain and service access
roads, headlands and drains. Additionally, attending to weed issues will aid in
the prevention of produce contamination, which affects the yield of the crops.
The reduction of weeds will prevent the amount of nutritional loss to crops, as
well as help to prevent pests and diseases spreading as they tend to use the
undesired plants as hosts. Furthermore, many weeds strangle cultivated plants
as they both compete for light, water and space. This reduces the amount of
desired vegetation, even if it is not intentionally farmed, which is used for
feeding livestock
2.
METHODOLOGY
2.1.
Preliminary Research and Design Parameters
This project
was initialised by determining the specific parameters associated with the ATV.
The plastic covers on the bike were removed revealing the gearbox, the shifter
selection lever and the connecting rod. This allowed initial tests to be
conducted, quantifying these parameters. Fig. 2 is a photograph of the vehicle
with its covers removed.
Fig. 2.
Exposed Yamaha Grizzly Side
While the
plastic covers were detached, the quad bike was operated to heat the
vehicle’s engine and sub-systems. The maximum temperature recorded was
470°C and was located at the front of the exhaust where the exhaust gases
first exit the engine. This was measured using a handheld thermometer gun
measuring the emissivity of an object. For comparison, measurements were taken
while the bike was cold. Additionally, a spring scale was used to measure the
force required to move the connecting rod. It was determined that 353 N was
required to initiate the movement of the rod from rest. Once moving, this
required force was reduced to 20 N.
The linear
movement of the connecting rod was determined to reach a maximum of 47 mm when
moving between the extremities (high range through to park). Further to this,
using a protractor, the angle of rotation of the mechanical gear selector
mechanism located on the outside of the gearbox was 70°. Based on this
information, research was conducted to determine the best solution to implement
an autonomous transmission system.
Fig. 3.
Mechanical Gear Selector Tab
2.2.
Proposed Design Solutions
A gear shifter
lever is used to change the positions of the selector forks to vary the
position of the gears. The manual force applied to the lever moves the
connecting rod and gear selection tab, activating one of five solenoids. This
movement is illustrated in Fig. 4. As the solenoid is activated, the internal
transmission fluid, which is pressurised, flows through the opened chamber
caused by the void left from the solenoid. This applies a force to a specific
clutch plate, which allows the desired energy paths to be obtained through the
planetary gearset. Attaching a linear actuator to the connecting rod,
installing a servomotor or rotating actuator as well as replacing the
transmission fluid pump with a computer-controlled fluid velocity device, were
all possible avenues that were explored to autonomously achieve transition of
the transmission.
Fig. 4. Gear
Shifting Motion
It was
concluded from the research conducted that it was not economical or viable to
replace the fluid pump inside the transmission box. To obtain a pump with the
specific geometry, speed and feedback inputs which are necessary for this
application would be extremely difficult. Additionally, there would be a
significant increase in the essential programming needed to satisfy the
predetermined parameters of the current factory pump.
Furthermore,
due to the limited available space, high temperatures around the engine and
gearbox and need for high levels of precision positioning of the servomotor, it
was determined that this solution would not be the best suited for the specific
application of autonomising an ATV.
Because of the
simplicity of implementation, as well as effectiveness and ability to absorb
any small inaccuracies related to distance measurements, it was concluded that
the linear actuator was the best solution to modify the standard 2017 Yamaha
Grizzly’s transmission into a fully autonomous system.
2.3.
Actuator Selection
There are many
different types of linear actuators which include but are not limited to electromechanical,
hydraulic and pneumatic. Through research and discussions with actuator
technicians and manufacturers, it was decided that the electromechanical type
was the most appropriate for this task. An electromechanical actuator was
chosen due to the achievable accuracy of increments, the low cost of
procurement, the minimum force needed to move the connecting rod, the benefit
of not requiring a pump or compressor as well as the low maintenance needs.
The accuracy
of the electromechanical actuator is directly related to the accuracy of the
potentiometer, the coarseness of the threaded rod as well as the velocity of
the shaft. Accuracy is defined by manufacturers as “the ability of an
actuator to achieve a specified position.” A standard actuator can obtain
an accuracy of ± 1mm provided they are installed correctly. This
accuracy is sufficient for this application as there is an additional degree of
alignment as the gear selector falls into the desired gearing mesh which
contributes to the overall self-alignment of the system. Further to accuracy is
repeatability. Repeatability is “the ability for an actuator to achieve a
given position time after time or repeatedly.” In most applications, the
ability to have greater repeatability is more important than the ability to
achieve high levels of accuracy [21].
Electromechanical
actuators come in a wide range of sizes and shapes, each with its force
capabilities. According to Donald Firesmith, to ensure an over-engineered
design a factor of safety (FOS) of 2.5 should be used [5]. Because of this, the
minimum required force capability of the actuator was determined to be 236 N.
Another design condition of the actuator was to have the ability to change
between the extremity positions in under 5 seconds (0.01 m/s). Additionally,
the resistance to heat, dust, water, vibration and impulse force were likewise
considered. Furthermore, the ability to comply with geometric restrictions, the
overall cost of the component, the time to receive the product and its
availability were all influencing factors when selecting the optimal solution
for the project. It was concluded that the best linear electromechanical
actuator to use as a prototype and proof of concept was the Motion Dynamics
HB-DJ806 - LALI10010. This was based on performance specifications,
availability of the item and the total price.
The HB-DJ806
is a small and compact unit, which can easily be mounted on the Yamaha Grizzly
without interfering with other standard or additional components on the
vehicle. Additionally, because of the actuator’s slim geometry, the
original plastic covers can be reinstalled to ensure aesthetics are maintained.
The
performance parameters of the actuator are; maximum stoke length 50 mm, speed
10.9 mm/s force capability 200 N and a voltage draw 12 volts while drawing
a maximum load of 3 amps. The actuator can be fitted with an internal
potentiometer to measure the resistance in the actuator and convert the values
to a position. This feature, however, endures an additional cost as well as increasing
the lead time by 8 weeks as they are made to order.
2.4.
Mounting the Actuator
Before
procurement, an approximation of the geometries of the HB-DJ806 actuator was
replicated using a full-sized 3D printed model, designed using SolidWorks 2017.
Due to the
limited geometries supplied by the manufacturer, the plastic printed replica
could only be approximately modelled. The supplied dimension for the height,
length and width were sufficient to manufacture a replica to determine the
exact mounting position, method and location. Once the functioning actuator
arrived, correct installation to the vehicle without complications was
achieved.
Initially, the
method to mount the actuator was to attach the fixed end to the tabs on top of
the chassis of the vehicle where the plastic housing for the shifter selector
lever was originally situated. It was secured using an M4 bolt and nut
attaching it to a rod-end, which is fitted to the mounting tabs of the frame.
The intent of the rod-end was to restrict the translational movement of the
actuator in all directions while maintaining its ability to rotate freely. The
connecting rod was shortened to account for the additional length provided by
the actuator and was attached to the shaft end of the actuator via a double
acting coupling.
For a robust and reliable
system to be developed, a new actuator was required. The device selected for
this application was the Linak LA14. This device is capable of withstanding
temperatures of 85°C, utilised a 12V DC motor, and could reach speeds of
36 mm/s while maintaining a load
level of 300 N drawing 2.6 amps. It also had a stroke length of 130 mm. This
device was rated to an IP66 standard, which is suitable for the intended
environment (Australian Outback).
Fig. 5.
Proposed Autonomous Transmission Solution
When Yamaha
manufactured the vehicle, a safety system was implemented to eliminate the risk
of selecting the reverse position while the ATV was moving forward, therefore,
removing the possibility of damaging the gears in the transmission box. This
safety measure was implemented by inserting a small bar between two groves on
the tab on the exterior of the gearbox as seen in Fig. 3. This created a
mechanical barrier, which prevents the reverse gear position to be selected without
engaging the brake to ensure motion was stopped. As the modification to the
transmission system will be controlled electronically via a computer, this
error will not arise, therefore, this factory safety measure will be removed to
simplify the communication between the autonomous gear and braking systems.
2.5.
Gear Selection Board
To select the
desired gear position (that is, park or neutral), it is proposed that a
5-button backlit board, similar to Fig. 6, is implemented. By utilising a
button board, it will be possible to achieve the aim of operating the vehicle
manually, remotely or autonomously. The hardware would remain constant for each
case with the variation arising with the method of supplying a signal to the
actuator to alter its position, thus, gear position. Additionally, when the
vehicle is operated manually, it will allow the driver to select the desired
gear without the need to manually cycle through the intermediate positions.
More so, as the buttons are backlit, the operator can visually see the current
gear position of the vehicle. This is used in conjunction with the standard
vehicle’s display. These features will contribute to saving time and
creating a more accessible design. The board will be positioned on the right-hand
side of the vehicle, on the upper wheel arch, in an easy to reach and
comfortable position for the operator. The board will be recessed into the
plastic body work creating an aesthetically pleasing finish.
Fig. 6. Gear
Selector Board
2.6.
Connectivity to the Main Operating System
The actuator,
along with the gear selection board will be connected to the CAMBUS via an
Ethernet transfer cable. It will be powered from an auxiliary battery used for
the additional accessories. Specific parameters are programmed once the
hardware is communicating and responding correctly to the operating system. To
complete a gear change, one of the 5-gear position buttons are activated,
causing the linear actuator to translate the appropriate distance. This will
engage the connecting rod, therefore, the selector plate. As the plate rotates,
it activates the solenoids inside the gearbox which are responsible for
altering the internal gearing position. Further to this, the ATV transmission
programming system will feature an automatic ‘park-engage’ system
when the ATV is started and stopped. This removes the risk of the vehicle
rolling away if unattended or if the operator forgets to move the gear position
to the park location. Additionally, when changing gears, the system will
automatically disconnect the current gear position and the corresponding
backlit button transitioning to the new required position, lighting the new
button. For extra safety and reliability of the design, the transmission system
will be required to communicate with the acceleration system to prevent gear
changes unless the ATV is stationary. This will also help to prolong the life
of the gearbox as grinding of gears will be eliminated.
2.7.
Testing, Modifying and Commissioning
Following the
implementation of the proposed solution, the final phase scheduled to be
completed to ensure functionality, safety and compliance is testing, modifying
and commissioning. The preliminary testing is initialised by varying the
actuator’s position in a controlled environment before it is connected to
the ATV. This is known as a bench test and is the safest and simplest method of
testing as it eliminates most of the associated risk. The exact ramped speed,
accuracy and repeatability of the system can be tested and modified before it
is placed under load when attached to the vehicle.
The secondary
testing consists of changing the gearing positioning while the bike is powered
down, again eliminating several risks and creating a simpler testing
environment. Modifications to the mounting angle, the distance of extension and
ramped acceleration speed will all be improved during this stage.
Once this
phase of testing has been completed and optimised, the following stage of
trials will commence while the bike is suspended and secured off the ground.
This is to prevent an incident from occurring if the newly implemented system
fails and the bike is unable to be controlled, causing damage and injury to the
surrounding equipment and bystanders. In this phase, the purpose is to test and
optimise the communication to alternate systems such as the brakes,
acceleration, display monitor and the main control system.
2.8.
Control System
An Arduino Uno
Board was used as it was simple to program and install. This type of
microcontroller was used for prototyping as it was simple to program and
install.
For the
prototype software only, an H-bridge was created using relay boards [27]. An
H-bridge changes the polarity on the DC motor within the actuator by changing
the flow direction of the current. This alters the direction of motion of the
actuator shaft, causing it to extend or retract. Two momentary buttons are
attached to the Arduino (Fig. 7), which are used to send a signal to the
processor, determining the appropriate combination of relays to be
activated/deactivated to achieve the desired movement.
Fig. 7.
Hardware (Prototype Proof of Concept and Prototype Testing Device)
3.
RESULTS AND DISCUSSION
3.1. Temperature
The temperature of the vehicle components (Gearbox, Exhaust, Heatshield,
Dump Pipe, Engine, Frame/Chasis, surrounds) were taken in two trials as shown
in Tab. 1. It was observed that temperatures around the gearbox and the engine
were around 100oC.
Tab. 1
Temperature
3.2. ANSYS FEA on Custom Made products
The
ANSYS FEA analysis was performed to determine if the design would achieve
infinite life criteria and perform correctly for the intended purpose. The
following table contains the summarised results from the analysis.
Tab.
2
ANSYS FEA result
Fig.
8. Original Bracket (Deformation, Strain, Stress, Stress (Zoomed),
Life and Safety Factor)
Fig.
9. Original Bracket (Deformation, Strain, Stress, Life and Safety Factor)
Fig. 10. Original mounting plate (Deformation, Stress, Life and Safety
Factor)
Fig. 11. Final Mounting Plate (Deflection, Stress, Life, Safety Factor)
Fig. 12. Mesh Sizing
The
mesh size used throughout the analysis was determined by comparing nine
different sizes from Fig. 8 to Fig. 11. The results were graphed in Fig. 12. A
6 mm mesh size was selected as it was the most accurate. The stress results
remain similar for mesh sizes from 7 mm through to 10 mm. At the 6 mm point,
the stress increases before dropping. According to literature, this point is
the most optimal for accuracy and computational speed and efficiency [16].
When
analysing the bracket in ANSYS, the actuator was fixed by applying a remote
displacement, the fixed end only allowing rotation in one direction. The
opposite end of the actuator had a remote force applied to the hole in the
shaft. The magnitude of this force was set using the component form. The
actuator bracket was fixed in place using remote displacement restricting
movement in all directions.
When
analysing the mounting plates, an additional component was added into the
assembly, which was used to apply the force. Originally, the force was applied
using a point load, however, it was clear that the result computed was
inaccurate and did not replicate the situation investigated.
It
was observed that the bracket would not achieve the desired infinite life
criteria and would fail. This was confirmed when cracking occurred after the
bracket was installed. The bracket was redesigned, reanalysed, and reprinted.
Although, the model showed that the new bracket was a suitable design, however,
it was limited in its ability to withstand heat, tighten the proof load of the
bolts sufficiently as well as oppose the extreme non-intended force due to the
physical properties of the plastic it was constructed from. Consequently, it is
recommended that for further use of this system, the bracket should be
constructed from a stronger material such as aluminium.
4. CONCLUSION
Due to the labour involved with eradicating weeds,
there is only a small increase in the profit margin if the crops are treated.
This cost could significantly be reduced by using an Autonomous vehicle capable
of deploying herbicide. As a result, an autonomous transmission system for a
2017 Yamaha Grizzly All-Terrain Vehicle was developed.
Preliminary tests found that
temperatures of around 100°C occurred around the gearbox and the engine.
Additionally, the travelled distance between the connecting rod and the gear
selection tab was 47 mm, which caused a 70° angle of rotation of the tab.
This motion required 7.06 Nm of torque to alter the gears mesh combination. The
force to move the tab was originally supplied by the shifter lever and
transferred its force through the connecting rod and to the gear selector tab.
At this point on the tab, the force required to change gears was 353 N. Using
these parameters, an electromechanical linear actuator was chosen as a
prototype device to simulate the input motion from the operator of the vehicle.
The Motion Dynamics HB-DJ806 - LALI10010 actuator was capable of exerting 200 N
at 35 mm/seconds. It had a stroke length of 50 mm and was powered by a 12V DC
motor, which drew 3 amps at maximum load.
The actuator was installed,
and an electric controller was developed using an Arduino Uno Board to drive
the actuator for testing.
The transmission system developed proved the
design concept, however, it was concluded that it was not a reliable and robust
system, which would achieve infinite life criteria. Subsequently, a larger,
stronger and faster actuator was purchased and installed. The new actuator was
capable of exerting 300 N at 36 mm/s while drawing 2.5 amps to its 12V DC
motor. Before procurement, this new actuator was digitally modelled using
SolidWorks 2017 and 3D printed to confirm the mounting position and method. To
mount the actuator and restrain its motion, a mounting plate and bracket were
manufactured from mild steel and plastic, respectively. The bracket was
designed and digitally model then 3D printed and installed. An FEA was
conducted on the custom-made components using ANSYS to ensure reliability. The
FEA suggested that the bracket would not achieve the desired infinite life
criteria and would fail. This was confirmed after cracking occurred following the
installation of the bracket. The bracket was redesigned, reanalysed, and
reprinted. Although, the model showed that the new bracket was a suitable
design, its ability to withstand heat, tighten the proof load of the bolts
sufficiently as well as oppose the extreme non-intended force was limited due
to the physical properties of the plastic it was constructed from. Accordingly,
it is recommended that for further use of this system, the bracket should be
constructed from a stronger material such as aluminium.
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Received 21.07.2020; accepted in revised
form 06.11.2020
Scientific
Journal of Silesian University of Technology. Series Transport is licensed
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