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The CVT is an automatic transmission that uses two pulleys with a steel belt running between them. To continuously vary its gear ratios, the CVT simultaneously adjusts the diameter of the "drive pulley" that transmits torque from the engine and the "driven pulley" that transfers torque to the wheels. With stepless shifting of gear ratios, the CVT can avoid the shift shock and deliver smooth driving, making it an exceptional transmission solution.

The CVT is an automatic transmission that uses two pulleys with a steel belt running between them. To continuously vary its gear ratios, the CVT simultaneously adjusts the diameter of the "drive pulley" that transmits torque from the engine and the "driven pulley" that transfers torque to the wheels. With stepless shifting of gear ratios, the CVT can avoid the shift shock and deliver smooth driving, making it an exceptional transmission solution.

CVTs differ from traditional automatic transmissions in that they don't have gears that provide "steps" between low- and high-speed operations. Instead, the majority of them work via a pair of variable-diameter, cone-shaped pulleys connected by a steel or composite belt. The halves of each pulley are aligned with the pointed ends of the cones touching. These form a V-shaped groove in which the connecting belt rides. One side of the pulley is fixed, and the other side is movable, actuated by a hydraulic cylinder. The cylinder can increase or decrease the amount of space between the two sides of the pulley. This allows the belt to ride lower or higher along the walls of the pulley, depending on driving conditions, thereby changing the "gear" ratio.

Study 1:

Case Study 1:

SIMULINK MODEL FOR BAJA ATV WITH CVT:

Input Signal:

The signal builder is used as input for brake, throttle and gear ratio. Brake input is maintained as 0 for overall simulation. The throttle input is given as 0.6 for20 secs and increases to 1.5 for overall simulation.

Engine:

Represents a system-level model of spark-ignition and diesel engines suitable for use at the initial stages of modelling when only the basic parameters are available. Optional idle speed and red line controllers are included.

The throttle input signal 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 the Stall speed, the engine torque is blended to zero. If the engine speed exceeds the maximum speed, the simulation stops and issues an error message.

Connections F and B are mechanical rotational conserving ports associated with the engine crankshaft and engine block, respectively. Connections P and FC are physical signal output ports through which engine power and fuel consumption rate are reported.

CVT Ratio:

Here the CVT ratio has decreased with respect to time. so it indicates that by increasing time the speed of the vehicle is increased because we increase the throttle input. so the CVT Ratio decreases with respect to speed & time.

The throttle valve is mainly to control the flow or amount of fuel into the engine, if the throttle value increases the flow of fuel increases to the IC engine which in turn increases the power of the engine. The gear ratio is linearly decreased to 0.8 and maintained constant for overall simulation as shown in figure

CVT Block diagram:

Variable Gear Ratio:

Represents a variable ratio gearbox such as implemented by mechanical belt CVT, electric, or hydraulic transmissions. The physical signal input r defines the ratio of input to output angular shaft velocities.

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.

Vehicle Body:

The throttle valve is mainly to control the flow or amount of fuel into the engine, if the throttle value increases the flow of fuel increases to the IC engine which in turn increases the power of the engine.

Case1:

Output

Throttle input increases the Velocity of the vehicle also increased rapidly. in this case, we have not applied brake throughout the cycle it remains zero. so the Velocity of the car has reached 60km/hr in 25 secs. then it mains 60km/hr throughout the cycle. Comming to distance the vehicle has travelled around 3Km in 3.3 Mins. so Trottle input players an important role in velocity acceleration.

Output for CVT Shaft:

change in Input speed of the primary shaft is also represented on the secondary shaft of the CVT.

STUDY 2:

SIMULINK MODEL FOR BAJA CVT USING DASHBOARD:

In this Simscape Model Throttle & Brake are adjusted during the cycle time.so we making the cycle as infinite. The remaining parameters are the same as the study1.This model is theoretical only possible. Brake inputs are not connected to the output display.

Output for CVT Shaft:

change in Input speed of the primary shaft is also represented on the output display secondary shaft of the CVT.

Output

Throttle input has decreased slowly so it is affecting the velocity of the vehicle also. After half cycle is completed the throttle remains constant so we are changing the brake value when a brake is applied on the vehicle so it affects the speed of the velocity of the vehicle.

Engine Torque Speed Curve:

From this graph, we can obtain that at 2700 to 3400 Engine RPM we will get the highest point of Torque. In the above figure, the torque is increasing by an increase in engine speed. At a particular point, the torque is decreasing when the gear ratio increases in order to achieve maximum velocity.

Study2:

Case1:

SIMULINK MODEL FOR BAJA CTV WITH LOOKUP Table (CVT ratio & RPM):

This is an Open system. In this system the input values of Throttle & Brake values are fed into the system. so the fuel runs the Engine continuously. Then Engine RPM have scenes and gives input to the Lookup table with respect to the Engine RPM, the gear ratio will be decided in the Lookup table. CVT will match its pulley diameter & Power transmission to the Gear Box. Gear shifts are automatically controlled by the CVT. From the gearbox, the power is transmitted to the Wheels

The signal builder is used as input for brake, throttle and gear ratio. Brake input is maintained as 0 for overall simulation. The throttle input is given as 0.7 for20 secs and increases from 1.2 to 1.6 for overall simulation.

Lookup Table:

Using this Look-up table the speed Vs CVT ratio is fed into the system. so the Output from the Engine sensor has connected to the Lookup table. According to the throttle input, the Engine speed varies so based upon the Engine Shaft Rpm THE gear ratio is fed into the CVT. Then it adjusts its transmission.

OUTPUT Display:

From this graph, you can notice that the brake is not applied in this cycle test. By applying the contact rate of 0.8 Throttle speed the speed gradually increases . After increasing the throttle the engine reaches the Maximum speed of 60Km/hr. Distance travelled by car in sec is 800Metres.

Output Display of CVT Shaft:

change in Input speed of the primary shaft is also represented on the output display secondary shaft of the CVT.

From this graph, we can obtain that at 2700 to 3400 Engine RPM we will get the highest point of Torque. In the above figure, the torque is increasing by an increase in engine speed. At a particular point, the torque is decreasing when the gear ratio increases in order to achieve maximum velocity.

Case2:

SIMULINK MODEL FOR BAJA CVT USING DASHBOARD & LOOKUP Table

This is the closed feedback system. in this system the output signal from the wheel is connected to the CVT input. So according to the Wheel speed, the Lookup table will choose the gear ratio as per the vehicle speed. Here the Lookup table output & CVT ratio are displayed as the output because it is not manually adjusted it will be adjusted by the Vehicle Speed by means of Throttle & Brake applied on the system.

LOOKUP Table:

As the input received from the Vehicle moving speed. The gear ratio has decided by the vehicle moving speed on the road. Depending on the Speed the gear ratio shifting happens in CVT. But this is the Costlier Method compared to the Open system.

CVT Block Diagram:

CVT Ratio:

In this diagram, we can notice that at starting of the Vehicle the speed of the vehicle is very low at that time the gear ratio is high at 1.8 but later when the throttle is starting to give the speed pickup & the gear ratio decreases & Vehicle reached its highest speed.

Vehicle Speed:

In this graph, we can notice that during the break applied is reduced from 0.5 to 0 so that the Speed started to increase later the brake is zero & throttle started to increase then the speed increased rapidly to a maximum speed of 60Km/hrs.

CVT Shaft Speed:

At initial, the vehicle speed is very low so the CVT reduces the speed of the output shaft. so you can notice that the secondary shaft RPM is lower than the primary shaft from the engine. So CVT adjusts the vehicle speed based on the Brake applied in the Initial stage. Later the brake applied is removed completely. Throttle giving to the engine also increased so that the CVT increases the final out of the secondary shaft speed rapidly.

Case 3:

SIMULINK MODEL FOR BAJA CTV MAPPED:

In this block, the Throttle values are increased at a regular interval of time. This is also a closed system with a Lookup table. Remaining all same as we discussed in the previous cases. The cycle time is 200 seconds.
Only in the case of the Lookup table, the graph will deviate with respect to the input & Output speed of the vehicle. Other than the CVT ratio fed into the Signal builder is a predetermined value results.

Throttle Input in Repeat sequence Stair command

Output CVT Ratio

CVT gear ratio decreases when the speed increases.

Output of Vehicle speed:

In this graph, we noticed that When the controller removes the brake from the car. the car starts moving by increasing the throttle every 20 seconds. After 80 seconds the Top gear shifts are achieved & and the car starts to move at a rapid speed.

The brake is applied at the initial condition only. later the brake is not applied in the cycle.

Conclusion:

Thus we have successfully analysed 5 different models of BAJA ATV WITH CVT and recorded the outputs: - (Vehicle velocity & CVT shaft rpm) with respect to variations in input throttle and brake.