Project

                                                   BAJA-All Terrain Vehicle(ATV) Model

AIM:

To study the model and carry out a system-level simulation of BAJA-All Terrain Vehicle model and study the characteristics of the model and prepare a detailed technical report about the simulation of the model under different conditions.

All-Terrain Vehicle:

Introduction:

An All-Terrain Vehicle(ATV), also known as a Light Utility Vehicle(LUV), a quad bike, or simply a quad, as defined by the American National Standards Institute(ANSI) is a vehicle that travels on low-pressure tires, with a seat that is straddled by the operator, along with handlebars for steering control. As the name implies, it is designed to handle a wider variety of terrain than most other vehicles. Although it is a street-legal vehicle in some countries, it is not street-legal within most states, territories and provinces of some countries. An ATV is also defined as a motorized off-highway vehicle designed to travel on four low-pressure or non-pneumatic tires. ATVs are subdivided into two types as designated by the manufacturer. Type I ATVs are intended by the manufacturer for use by a single operator and no passenger. Type II ATVs are intended by the manufacturer for use by an operator and a passenger, and are equipped with a designated seating position behind the operator. Similarly, riders must also consider the various ATV sizes. ATVs are "one size fits all". The ATV industry recommends all riders operate an ATV intended for their age. Youth model ATVs are designed for smaller hands and feets and travel at slower speeds appropriate for their age. As we said about ATVs having provision for operator and a passenger, some companies have developed such ATVs and these ATVs are also referred to as tandem ATVs. The rider sits on and operates these vehicles like a motorcycles, but the extra wheels give more stability at slower speeds. Although most are equipped with three or four wheels, six-wheels exist for specialized applications. Multiple-user analogues with side-by-side seating are called utility terrain vehicles(UTV) or side-by-sides to distinguish the classes of vehicle. Both classes tend to have similar powertrain parts. Engine sizes of ATVs currently for sale (as of 2008 products) range from 49 to 1000 cc.

History of ATVs:

The history of ATVs begin back in the 19th century, Royal Enfield built and sold the first powered quadracycle in 1893. It had many bicycle components including handle bars. The Royal Enfield resembles a modern ATV-style quad bike but was designed as a form of horseless carriage for road use.

Six-wheeled AATVs:

The term "ATV" was originally coined to refer to non-straddle ridden, typically six-wheeled amphibious ATVs, such as the Jiger produced by the Jiger Corporation, the Amphicat produced by Mobility Unlimited Inc, and the Terra Tiger produced by the Allis-Chalmers Manufacturing Company in the mid 1960s and early 1970s. With the introduction of straddle riddenATVs, the term AATV was introduced to define the original amphibious ATV category.

ATC development:

This type being directly influenced by earlier six-wheeled AATVs of the sixties, it utilized balloon tires for both a low environmental impact and to compensate for a lack of mechanical suspension. Honda entered the 1980s with a virtual monopoly in the market, due to effective patents on design and engine placement. By 1980, other companies would pay patent royalties to hinda to enter the lucrative ATC field with their own machines. Yamaha introduced their first ATC, the Tri-Moto YZ125. Kawasaki followed suit the next year with the KLT200, while Suzuki produced their first effort ALT125, in 1982. As the popularity of ATCs increased dramatically, rapid development ensued. As other manufacturers were entering the market, Honda was diversifying offering the ATC250R the first sport ATC intended for competition in 1981. The 1982 Honda ATC200E Big Red was a landmark model. It featured both suspension and racks, making it the first ATC designed specifically for utility and would become the world's best selling ATC. Honda followed that effort in 1983 with the ATC200X, an easy-to-handle 192cc four-stroke sport ATC that was ideal for new riders. Not to be outdone, Kawasaki and Yamaha responded with their own sport ATCs. 1984 saw the release of the Kawasaki KXT250 Tecate, and Yamaha followed in 1985 with the Tri-Z 250. Both were liquid cooled 250cc two-strokes capable of giving the honda ATC250R competition. In response to growing market, American Speciality manufacturer Tiger also introduced a series of ATCs Hand-built-to-order models that included the Tiger 500, the largest displacement ATC produced commercially. Honda continued to diversify their line-up releasing the larger fully suspended 250cc Big Red Utility ATC and introduced the 350X sport ATC their largest displacement machine in 1985. American based manufacturers also produced ATCs in this period, albeit in small numbers. Polaris offered the Scrambler in 1985 and 1986, producing appx 1600 units. Speciality manufacturer Tiger ATV also produces a range of ATCs but their liquidation in 1991 left no official record of how many units were produced. Tiger ATCs were offered for three years with models using 80 to 500cc two-stroke engines provided by KTM and Rotax. The Tiger 500 is notable for being the fastest consumer ATC available with tested top speeds of +80mph from the stock 42 horsepower at 6500rpm engine and 5 speed gearbox.

Four-wheelers(1980s-Today):

Suzuki was a leader in the development of mass production four-wheeled ATVs. It sold the first model the 1982 QuadRunner LT125 which was a recreational machine for beginners. Adventure Vehicles of Monroe, Louisiana made the first quad ATV in 1980. They called it the Avenger 400. Prior to that, Adventure Vehicles made 3 wheel ATVs and a dump body utility 3 wheeler using Kohler 8hp engines and Comet drive systems. The Avenger 400 was a rigid suspension vehicle with a fibreglass body and welded tube construction. It was a rudimentary vehicle reminiscent to the Tote Gote of the 1960s. Suzuki sold the first four-wheeled mini ATV the LT50 from 1984 to 1987. After the LT50, Suzuki sold the first ATV with a CVT transmission the LT80 from 1987 to 2006. In 1985 Suzuki introduced to the industry the first high-performance four-wheel ATV, the Suzuki LT250R QuadRacer. This machine was in production for the 1985-1992 model years. During its production run, it underwent three major engineering makeovers. However, the core features were retained. These were:

1) A sophisticated long-travel suspension.

2)  A liquid cooled two-stroke motor.

3) A fully-manual five-speed transmission( for  1985-1986 models).

4) A six-speed transmission( 1987-1992 models).

It was a machine exclusively designed for racing by highly skilled riders.

Honda responded a year later with the FourTrax TRX250R a machine that has not been replicated until recently. Kawasaki responded with its Tecate-4 250. The TRX250R was very similar to the ATC250R it eventually replaced and is often considered one of the greatest sport ATVs ever built. In 1987 Yamaha Motor Company introduced a different type of high performance machine the Banshee 350 which featured a twin-cylinder liquid-cooled two-stroke motor from RD350LC street motorcycle. Shortly after the release of Banshee in 1987, Suzuki released the LT500R QuadRacer. This unique quad was powered by a 500cc liquid-cooled two-stroke engine with a five-speed transmission. This ATV earned the nickname "Quadzilla" with its remarkable amount of speed and size. Models continue today to be divided into the sport and utility markets as these machines are popular with hunters, farmers, ranchers and workers at construction sites. Sport models are generally small, light, two-wheel-drive vehicles that accelerate quickly, have a manual transmission and runs at speeds upto approximately 80mph. Utility models are generally bigger four-wheel-drive vahicle with a maximum speed of upto approximately 70mph. They have the ability to haul small loads on attached racks or small dump beds. They may also tow small trailers. Due to the different weights, each has advantages on different terrain. A popular model is Yamaha's Raptor 700, which features a nearly 700cc four-stroke engine. 

Six-wheel models often have a small dump bed, with an extra set of wheels at the back to increase the payload capacity. They can be either four-wheel-drive or six-wheel-drive. In 2011 LandFighter was founded, "the first Dutch/European ATV brand". The largest part of production takes site in Taiwan to European standards the ATVs are finally assembled in the Netherlands.

Safety Concerns of ATCs:

Safety courses and educational literature has reduced the number and severity of accidents among ATC and ATV riders. As cornering is more challenging on an ATC than with a four-wheeled machine, properly leaning into the turn is required to counterbalance the weight and keep the machine stable. Operators may roll over if caution isn't used at high speeds. The lighter front end and smaller footprint of ATCs present both a flipping and steering hazard under acceleration and on inclines. Lateral rollovers may also occur when traversing steep inclines. However, in most terrain with the proper riding technique and safety gear, this issues can be mitigated. ATCs require unique techniques to ride properly and turning lean requires more exaggeration than ATVs; Throttle steering is another technique commonly used on ATCs in soft terrain and at high speeds, leaning to the inside of the turn and manipulating the throttle to break traction with the rear tires, resulting in the machines turning on axis while maintaining a forward direction.

Applications of ATVs:

ATVs are used in agriculture to bridge the advantages of trucks and tractors. They are used in a variety of industries for their maneuverability and off-roading ability. These include:

• Border Patrol
• Construction
• Emergency Medical Services
• Land Management
• Law Enforcement
• Military
• Mineral and Oil Exploration
• Pipeline Transport
• Surveying
• Wild Land Fire Control

Continuously Variable Transmission:

A continuously variable transmission (CVT) is an automatic transmission that can change seamlessly through continuous range of gear ratios. This contrasts with other transmissions that provide a limited number of gear ratios in fixed steps. The flexibility of a CVT with suitable control may allow the engine to operate at a constant RPM while the vehicle moves at varying speeds. CVTs are used in automobiles, tractors, motor scooters, snowmobiles and earthmoving equipment. The most common type of CVT uses two pulleys connected by a belt or chain however several other designs have been used at times. The figure below shows the digram of a common type CVT consisting two pulleys connected via a belt. The CVT consists of following parts:

1) Primary Pulley

2) Variator

3) Secondary Pulley

4) Belt

The variator is connected to both primary and secondary pulleys, when the variator connected to the primary pulley moves outwards, then the variator of the secondary pulley move inwards such that the radius of the primary pulley is less than the radius of the secondary pulley which leads to speed reduction and when the variator connected to the primary pulley moves inwards, then the variator of the secondary pulley moves outward such that radius of primary pulley is more than the radius of the secondary pulley which leads to the overdrive condition.

THEORY:

BAJA-ATV MODEL:

The model for Baja ATV is given below in the attachment. Here, we have four models of Baja ATV based on the input given and also the connection type, in otherwords, we are using both open-loop and close-loop configuration.

Baja-ATV Model-1(Without Lookup Table and Dashboard):

As per the circuit diagram below in the attachment, the following are the blocks used:

1) Signal Builder:

Here, we have used two signal builders. Signal builder as we already know is used for generating input signal for the model. Here, one signal builder is used for representing the brake and throttle inputs. Here, the brake input signal is given at 0. The throttle input at first is given as 0.3 upto 20 seconds. After 20 seconds, the throttle input is set to the value 1 for the remaining time. The waveforms of brake input and throttle input are given in the attachment below.

2) Generic Engine:

The Generic Engine block represents a system-level model of spark-ignition and diesel engines suitable for use at initial stages of modeling when basic parameters are available. The block parameters of generic engine is given in the attachment below. Optional idle speed and red line controllers are included. The throttle input T lies between zero and one and specifies the torque demanded from the engine as a fraction of the maximum possible torque. If the engine speed falls below stall speed the engine torque is blended to zero. If engine speed increases beyond the maximum speed then the simulation will stop and issues an error message. The values of the speed vector and torque vector is obtained from the diagram and logged the values in the workspace of MATLAB file. The below attachment shows the values of the speed and torque vector values in the workspace and the speed torque graph.

3) Engine Sensor:

The engine sensor block is actually a subsystem in which it consists of an idean rotational motion sensor, two PMC ports, mechanical rotational reference, PS Terminator which is used for terminating the physical signal outputs and a scope for viewing the engine RPM for the given simulation time. Here, the two PMC ports are connected to the F and B port of the generic engine, which are the mechanical rotational conserving ports. It senses the engine rpm and is connected to the CVT blockset. The curve representing the engine rpm is given in below attachment.

4) CVT Blockset:

The CVT blockset consists of two inertia blocks representing input shaft inertia and output shaft inertia respectively, a Variable ratio gear, two ideal rotational motion sensors and PMC ports. Input shaft represents the primary pulley and output shaft as the secondary pulley and mechanical rotational sensor is connected to input and output shafts and variable ratio gear represents a variable ratio gear box such as implemented by mechanical belt CVT, electric or hydraulic transmissions. The physical signal input defines the ratio of input to output angular shaft velocities. Connections B(Base) and F(Follower) are mechanical rotational conserving ports. The CVT ratio specifies the relation between base and folower rotation direction with the output shaft rotates parameter. The CVT ratio is also generated by the signal builder. The graph depicting the CVT ratio is given below attachment.

5) Simple Gear:

This block represents a fixed ratio gear or gear box. No inertia or compliance is modeled in this block. The output from the CVT block is connected to the simple gear. You can optionally include gear meshing and viscous losses. Connections B(Base) and F(Follower) are mechanical rotational conserving ports. Specify the relation between base and follower rotation directions with the output shaft rotates parameter. The attachment consist of block parameters of simple gear. 

6) Vehicle Body:

This block reprresents a two axle vehicle body in longitudinal motion. The block accounts for body mass, aerodynamic drag, road incline and weight distribution between axles due to acceleration and road profile. The vehicle can have same or different number of wheels on each axle. Optionally include pitch and suspension dynamics or additional variable mass and inertia. The vehicle does not move vertically relative to ground. The block parameter is given on the attachment. Here, port H represents the mechanical translational conserving port associated with the horizontal motion of the vehicle body. Connections V, NF, NR represents the physical signal output ports for vehicle velocity, normal front and normal rear wheel force respectively. Inside the Vehicle body subsystem we have tyre block which represents the logitudinal behavior of a highway characterized by the tire Magic Formula. The parameters for tyre block is given below. We also have used a Double-Shoe Brake block which represents a brake arranged as two pivoted rigid shoes symmetrically installed inside or outside a drum and operated by one actuator. The actuator force causes the shoes to exert a friction torque on a shaft connected to the drum. The parameter of double-shoe brake is given below.

7) Scope:

We have provided three scopes, one for the engine rpm, second for the vehicle speed, throttle input and brake input and third for the CVT shaft rpm.

INPUT :

As we said earlier, the simulation model consist of two signal builder blocks for providing input. One is for the brake and throttle input and the other is for the CVT ratiio which is given input to the CVT subsystem, for the variable ratio gear. We have also provided the Brake input and Throttle input waveforms and also for the CVT ratio waveforms in the attachment below. Now, coming to the input signals, we are giving the brake input as 0 for 200 seconds, which is the simulation time(here, on the signal builder, we have set the time axes limit to 80 seconds). It remains constant, there is no variation for the signal. 

Coming to the case of Throttle input, the initial value is 0.3 upto 20 seconds which represents the throttle is in the minimum position or off condition. At 20 seconds, the throttle value is set to 1, which represents that we have applied the throttle and this remains constant.

CVT Ratio:

The CVT ratio is set at the value of 3.5 for the first 5 seconds. After 5 seconds, the CVT ratio decreases in a linear fashion to 0.5 at 35 second and remains constatnt value of 0.5 for the rest of the time.

Here, the variation in the speed curve of the vehicle and for the change in engine rpm at the start is due to the throttle input. When the throttle input is set to 1, similarly, the CVT ratio changes after 5 seconds, this change is reflected in the waveforms of the engine rpm, CVT primary and secondary shaft rpm and the velocity of the vehicle. Here, by changing the gear ratio of the simple gear, it is observed that eventhough, waveforms of engine rpm, CVT primary and secondary shaft rpm, vehicle speed remain same, but the final values of the parameters changes. This is evident in the data inspector results provided in the attachment below. 

OUTPUT:

The output curves are shown below in the data inspector file in the attachment.

Velocity and Vehicle body Curve:

We have simulated the model for different gear ratio and for different vehicle body mass. We have checked the characteristics for gear teeth ratio of 8 to 14 with vehicle body mass of 100kg to 250kg. So, we have observed the changes in the CVT primary and secondary shaft rpms for respective gear ratio and also for vehicle masses. It is evident for the case of vehicle velocity characteristics, when we observed on same gear ratio with different vehicle body mass, we observed a small change in final velocity attained by the model at 200 seconds. This is because, when the mass of the vehicle increases, the speed decreases. This is because the engine has to work more to attain the constant speed. Even though the initail velocity is same for the same gear ratio with different masses, the curve can be explained like, when at gear ratio 8, the initial velocity is the highest of all and when we set the gear ratio 14, the initial velocity became lowest seen. It can be seen that when gear ratio of simple gear increases, the initial velocity decreases. This is because, a lower gear ratio provides a higher top speed and a higher gear ratio provides faster acceleration. So, from 0 second to 20 second, the speed rises in a somewhat linear fashion. After 20 seconds, this is when we set the throttle input value to 1. So, at this point of time, the speed will increase with acceleration. When the gear ratio is high, acceleration incerases which is seen s drastic increase in the speed upto a peak value. This is due to the variation of the throttle input. But when the throttle input is constant, the speed aster this peak value or peak point remains constant. 

For the case of lower gear ratio that is below 8 say when we appled gear ratio as 2, the same happened only difference is that due the change of throttle input, the velocity rises to a peak value but after that, the velocity of the model fall to zero. This is because the engine does not have enough torque. 

CVT Primary and Engine RPM:

Both the CVT primary and the engine rpm curves are similar because the engine is connected to the primary shaft of the CVT. Here, as said above we simulated the curve for different gear ratio and mass of the vehicle body. Here, the initial values are same for every case. This is because we have set the value for initial rpm as 1600 rpm in the generic engine block parameter. So, at the start of the simulation time, the engine rpm is 1600 rpm. Then for upto 20 seconds the rpm varies linearly. At 20 seconds, the throttle input is set to 1, so there is a sudden increase of the rpm upto 30 seconds, then the rpm falls and then increases steadily upto 100 second. After 100 seocnds, the rpm values becomes constant. Here, when the gear ratio increases, the final rpm value also increases. 

CVT Secondary RPM:

Here, the curve starts at 455-460 rpm initially. Upto 20 seconds, there will be slow increase in the rpm of the secondary shaft of the CVT. After 20 seconds, there will be sudden rise in the rpm. This is due the throttle value set to 1. Like the velocity curve and the CVT primary shaft curve, the rpm increases to the peak value at about 35 seconds. After that, the rpm value attains constant value. Here also, like above parameters, the final rpm of the secondary shaft of CVT increases with increase in the gear ratio. But decreases with increase in vehicle body mass for the same gear ratio. This  can be observed in the data inspector file attachment.

Baja-ATV Model-2 With Dashboard(Without Lookup Table):

A simulink model of Baja-ATV with dashboard is given below in the attachment. The rest of the blocks used are same as above. We have added few blocks and they are explained below.

Dashboard:

A dashboard or dash or instrument panel or fascia is a control panel usually located ahead of a vehicle's driver displaying instrumentation and control for the vehicle's operation. Generally, the dashboard consists of information about speed of the vehicle, fuel level of the vehicle, indicator and light mode details(wether high beam or low beam in the case of light and for indicator, left indicator or right indicator is on or off).

The initial conditions are as follows:

Brake input= 0

Throttle input= 0.3

INPUT:

It comprises a throttle and brake input as above but we have provided these inputs through a knob which can be varied unlike the signal builder in the previous model without dashboard. The engine rpm and Velocity curves displays changes as a result of the changes applied to the knobs. We have set the simulation time as infinity so that we can vary the input during the run time. 

OUTPUT:

The output curves of Baja-ATV with dashboard is given below in the attachment. As from the curves, the variations in the parameters such as CVT primary rpm, CVT secondary rpm, velocity, vehicle body and the engine rpm varies the same as in the case of above model. The only difference between these models are that in the first model, the brake input and the throttle input were constant values. They were predefined using signal builder. That is why we got the same nature of the curve that is the same shape with less initial and final values for lesser gear ratio. In this model, as the input given is of varying type, which we are varying during the run time, even though the wave shape is somewhat similar but the nature that is, for higher gear ratio, the value for final CVT primary and secondary rpms and engine rpm, velocity also decreases. In the case of different masses of the vehicle body, under same gear ratio, the same happens. The waveforms for all the parameters which also include the throttle input and brake input is given in the data inspector file in the below attachment.

Baja-ATV Model-3 With Look-up Table(Without Dashboard):

A simulink model of Baja-ATV with Look-up Table without dashboard is shown below in the attachment. Here, we are providing or uploading a look-up table for datas or values for the CVT ratio. 

Look-up Table:

A look-up table is an array of data that maps input values to output values, thereby approximating a mathematical function. Given a set of input values, a look-up operation retrieves the corresponding output values from the table. If the look-up table does not explicitly define the input values, then Simulink can estimate an output value using interpolation, extrapolation or rounding.

Interpolation: It is a process for estimating values that lie between known data points.

Extrapolation: It is a process for estimating values that lie beyond the range of known data points.

Rounding: It is a process for approximating a value by altering its digits according to a known rule.

A look-up table block uses an array of data to map input values to output values, thereby approximating a mathematical function. Given a set of input values simulink performs a look-up operation to retrieve the corresponding output values from the table. If the look-up table does not define the input values, the block estimates the output values based on nearby table values. In place of CVT ratio input, a lookup table is assigned inthe model below. It needs to be loaded in the workspace having the file name as- "LookupTable_data.mat".

CVT Ratio v/s Vehicle Speed:

At the starting, that is at 4km/h, the CVT ratio is 3.5. Now, from the graph, as the speed increases, the CVT ratio is decreasing. Here, from the graph, at 10km/h, the CVT ratio is 1.5. Further increase in speed the CVT ratio decreases even further. From the graph, at 34.4km/h, the CVT ratio becomes 0.5. Beyond this vehicle speed, as the speed increases, the CVT ratio remains constant with the value 0.5.

INPUT:

They are given in steps using the step block. The parameters are as follows:

Brake Input:                                                                        Throttle Input:

Step Time: 35seconds                                                           Step Time: 20seconds

Initial Value: 0seconds                                                           Initial Value: 0.3second

Final Value: 0seconds                                                             Final Value: 1second

Sample Time: 0seconds                                                          Sample Time: 0second

OUTPUT:

The output of the simulation of the Baja-ATV with Look-up Table without Dashboard is given below attachment which is the data inspector file which contain curves of parameters such as the CVT ratio, CVT primary rpm, CVT secondary rpm, engine rpm, vehicle velocity for different gear ratio and mass of vehicle body. Like early models, here also, when the vehivle mass increases, the final values of the velocity decreases. When the gear ratio increases, the CVT primary and scondary rpm final values also increases.

Baja-ATV Model-4 With both Look-up Table and Dashboard:

The simulink model of Baja-ATV model with look-up table and dashboard is given below in the attachment. 

 INPUT:

It comprises a throttle and brake input through a knob which can be varied unlike the step input block like in the previous model without dashboard. The engine rpm and velocity gauge displays the changes done by respective knobs. The initial conditionfor this model is same as that of the simulink model without look-up table. We use the same look-up table for this model also. We have set simulation time as infinity because we have to vary the throttle and brake input knobs inorder to observe the curve. By this, we can give input during runtime of the model.

OUTPUT:

The output curves of Baja-ATV with look-up table and dashboard is given below in the attachment. As from the curves, the variations in the parameters such as CVT primary rpm, CVT secondary rpm, velocity, vehicle body and the engine rpm varies the same as in the case of above model. The only difference between these models are that in the first model, the brake input and the throttle input were constant values. They were predefined using signal builder. That is why we got the same nature of the curve that is the same shape with less initial and final values for lesser gear ratio. In this model, as the input given is of varying type, which we are varying during the run time, even though the wave shape is somewhat similar but the nature that is, for higher gear ratio, the value for final CVT primary and secondary rpms and engine rpm, velocity also decreases. In the case of different masses of the vehicle body, under same gear ratio, the same happens. The waveforms for all the parameters which also include the throttle input and brake input is given in the data inspector file in the below attachment.

CONCLUSION:

Hence the given Baja-ATV model were simulated successfully and from the above results, we can conclude:

• Velocity, CVT Shaft speed and Engine speed are directly proportional to the throttle input and inversely proportional to the brake input.
• CVT ratio is directly proportional to Torque and inversely proportional to Throttle input.
• CVT secondary speed is greater than the primary speed.

 REFERENCE:

BAJA ATV Model File(https://www.mathworks.com/matlabcentral/fileexchange/70576-baja-all-terrain-vehicle-atv-model)