BAJA ATV Model_simulation_Project

AIM: 

• To do a system-level simulation of all Terrian vehicles.
• To study the performance or the behavior of different CVT Models given and do the detailed report of results.

Description:

In BAJA SAE, engineering students are tasked with designing and building a single-seat, all-terrain sporting vehicle that is to be a prototype for a reliable, maintainable, ergonomic, and economic production vehicle that serves a recreational user market. The students must function as e team to design, engineer, build, test, promote, and compete with a vehicle within the limits of the rules.

Team synergy racing is a student design competition team of G L Bajaj Institute of Technology and management participates in Mini BAJA competitions organized by SAE where students showcase their designs of off-road vehicles that can challenge rides on rough Terrians, water bodies and could survive. These vehicles are judged on sales, design, safety, and cost. They also raced to determine performance capability in acceleration, hill climb, maneuverability. To ensure the vehicle performs well in the competition and be completed in time, structured designs were used to define customer needs, create the product specification and make conceptual design decisions.

 

Designing and manufacturing the continuously varying transmission(CVT).

A continuously variable transmission(CVT) is a transmission that can gradually shift to any effective gear ratios between driver shaft and driven shaft within a set upper and lower limit which leads CVT to operate the engine at high combustion efficiency.

The CVT is designed considering the requirements of the SAE BAJA event. This gearbox provides better acceleration and ease in handling as compared to the manual transmission and cost-effective as compared to the other transmission available in the market. Being environment friendly, CVT is chosen as the best option to balance fuel economy and vehicle performance replacing conventional gearbox transmission. With different gear ratios between a drive shaft and a driven shaft, a CVT permits the engine to perform at high combustion efficiency resulting in lower emissions and higher fuel economy. In general, any automobile has only 4 to 6 specific gear ratios which can be selected whereas CVT provides Infinite variable gear ratios which allow the engine to maintain a constant speed while the vehicle increase in velocity. This results in better vehicle performance if the CVT is shifted such that the engine is held at the RPM that runs most efficiently at and produces the most power. Since there are no steps between effective gear ratios, CVTs operate smoothly with no sudden jerks commonly experienced in manual transmission.

CVT has been proved to be an efficient and cost-effective method of power transmission. The application of CVT products include

Snowmobiles to Dune Buggies

Cement Trowlling Machines

Electric vehicles

Agriculture Equipment

Construction Equipment:

CVT consists of Drive Pulley, Driven Pulley, and matching “V” Belt. This system does convert torque through changing pulley ratios automatically and continuously with changes in RPM and load or torque demand which acts as an automatic clutch and variable ratio transmission.

 

The drive pulley is mounted on the engine and is a speed-sensitive device that acts as a delayed clutching mechanism for low-free engine starting and idling.

At a predetermined RPM, the sliding half of the pulley engages the belt and transmits RPM and torque to the driven pulley. As a result, the position of the belt moves from a very small radius to a large radius, thereby affecting a change in pitch diameter and therefore the pulley ratio. The driven pulley is torque-sensitive enables this two pulley system to automatically adjust to the correct ratio for a given load.

The driven pulley or secondary pulley receives the turning of the belt from the drive pulley. As result, the position of the belt moves from a large radius to a smaller radius.

BAJA ATV Models:

1. BAJA_cvtModel
2. BAJA_cvtModel_Dashboard
3. BAJA_cvtModel_cvtratio_rpm
4. BAJA_cvtModel_dashboard_mapped/CVT
5. BAJA_cvtModel_mapped
6. BAJA_cvtModel_data

                       CVT- Gear Box

 

       BAJA ATV _cvt_Model:

Signal Builder Block: Using this block the brake input signal and the throttle input signal of values 0 and 0.3 respectively provided to the engine block. Throttle input will control the fuel consumption by the engine such that torque-speed input data is provided to the engine. So the required value of torque at a defined speed is produced by the engine with a sufficient amount of fuel consumption.

                  

                                                             

                      Signal Builder Block                         Input  Signal

Generic Engine:  It represents a general internal combustion engine. This block is suitable for a generic engine for spark ignition and diesel. Speed –power and speed-torque parametrizations are provided. Using this block we can calculate torque and speed through the block programmed formula by taking throttle signal as input. The block also engines power using a function of engine speed, g(rho).

The normalized throttle input signal T specifies the actual engine power as a fraction of maximum power at a fixed speed.  The engine torque is τ=p/Ω

Input: T-Normalised engine throttle level-Engine Torque demand as a fraction of maximum possible torque.

Output: P-Instantaneous engine power,W-power produed by engine,in W

FC port- Fuel consumption rate,kg/s

B port-Engine block: Mechanical rotational conserving port associated with the engine block

F port-Engine Crankshaft: Mechanical rotational conserving port associated with the engine crankshaft.

Engine sensor:

 

    

                 Motion Sensor Subsystem                          Motion sensor Block

 

This block measures angular velocity or angle in a mechanical rotational network. The physical signal ports W and A report the angular velocity and angle, respectively, of port R relative to port C. The measured angular velocity is positive when the angular velocity at port R is greater than the angular velocity at port C.

The thermistor is connected to terminate any physical signal outputs. Unconnected Physical signal output port does not generate warnings, but a connection to a PS Thermistor can be used to indicate that the signal was not inadvertently left unconnected.

Scope of Engine RPM: determines the engine speed and is provided as input to CVT block. The speed of the engine is 3400rpm after 40 seconds.

 

 

CVT,  continuously varying transmission gear:  It represents a variable ratio gearbox, which implements a push belt continuously variable transmission(CVT) with independent radii control. we can use this block for control system design, powertrain matching, and fuel economy studies. 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. The input and output shafts rotate in the same direction. No transmission and viscous losses are considered.

               In this model of CVT, two spinning inertias are connected to the input shaft and output shaft of the variable transmission gearbox. The inertias spin with the different angular velocities along with the two shafts that are coupled by a gear. These inertias will experience different torques. They are actuated by an external torque produced by the engine through the engine sensor block. Engine sensor block is connected such that the initial velocities of both the shafts are set to zero and the default follower-base gear ratio value to 10. The CVT block accepts the continuously varying gear ratio as a physical Simulink signal through the extra physical signal input labeled ‘r’. So we need to create a variable signal for the gear ratio with a Signal Builder from the Simulink block library and Simulink-PS Converter block. Build a signal that rises with a constant slope from 1 to 4 over 10 seconds. Then connect the converted physical signal to the r port.

We need not change the other, original settings of the simple gear model. The angular velocities and torques of the two shafts have the same signs. The ratio of angular velocities and torques will be at 10, as the gear ratio is set at 10. As the gear ratios decrease towards 1, the angular velocity of inertia 2 becomes greater than the velocity of inertia 1 while the associated torque in the second shaft becomes smaller than the torque in the first shaft. Because the gear ratios changing, the motion and torque do not follow the sine wave.

Due to other vehicle parameters, the inertia rotational torque values may vary from the provided engine torque value. The CVT plays an important role in manipulating these torque values of shafts to bring to the fixed gear ratio provided by the simple gear. By doing this the fuel consumption by the engine will be reduced and the performance of the engine will be improved.

To create this model, from Simcape driveline, simscape, and Simulink block libraries, drag and drop two inertia, two ideal rotational motion sensor, two mechanical rotational references, and two PS-Simulink Converter and from simscape utility library, drag a solver configuration block which is mandatory for every distinct driveline block diagram. CR tag provides the CVT ratio from the Signal Builder block to the subsystem CVT. The ideal motion sensors will measure the angular velocities of two shafts and are tagged to Goto blocks, Primary and Secondary tags such that data can be displayed by a scope block using Form tags, Primary and Secondary. Form tags receive data from Goto tag by connecting with visualize signal(wifi signal)

    

                                           CVT  subsystem Model                                                       CR

 

   Plot of Primary and secondary shaft speed:

 

     

 

        3D-Model of CVT Transmission Gearbox:

                              

 

 Input data to Engine:

                       

Output results: Vehicle speed, distance are plotted against time. The results determine that within 20 seconds the vehicle has attained a maximum speed of 60km/hr and the distance traveled is 8000m

                       

 

 

Vehicle Body subsystem: This block represents the longitudinal behavior of a highway tire characterized by the tire Magic Formula. The block is built from Tier-Road Interaction and Simscape Foundation Library wheel and Axle blocks. The effects of tire inertia, stiffness, and damping can be included.

Connection A is the mechanical rotational conserving port for the wheel axle.

Connection H is the mechanical translational conserving port for the wheel hub through which the trust developed by the tire is applied to the vehicle.

Connection N is a physical signal input port that applies the normal force acting on the tire. The force is considered positive if it acts downwards.

Connection S is a physical signal output port that reports the tire slip.

Connection M is optionally exposed physical signal ports set to parameterize by physical signal Magic Formula coefficients.

Connection W is the wind velocity

Double-Shoe Brake: This block 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.

Connection S is a conserving rotational terminal associated with the drum shaft.

Connection F is a physical signal port representing the force input to the actuator. Positive force creates friction torque that resists shaft rotation.

The output inertia shaft motion generated by the gearbox will be transmitted to the wheel axles of the front and rear. simulation is done to measure the vehicle velocity and distance the vehicle traveled. From tags are connected to output block where the data is received from Goto tags v and d connected in-vehicle body subsystem. Constant blocks C are connected one for the inclination and the other for wind velocity.

 

BAJA ATV Model with Dashboard:

In this model, a dashboard is provided with two custom gauges from the simscape library by drag and drop option, one for visual display of RPM and the other for velocity where we input data manually. Similarly, we drag and drop Knob blocks from the library for brake input and throttle input. Instead of Signal builder, we connect constant blocks to input brake value and throttle value.

 

            

 

We can select the value on the dashboard like brake input equals zero and throttle input equals 0.5. we should select the button under connection in the knob pop-up window to avail the connection between the knob and Simulink model and can feature the knob with desired values.

 

 

                   

 

Similarly here also we need to provide a connection between the velocity knob and Simulink model by selecting the radio button under connection and enter the desired visual data values

 

 

 

On simulation, the below plot diagram displays the behavior of required output, the primary and secondary shafts speed, velocity, and distance traveled by the vehicle. The output results can be seen in the dashboard. The speed of the engine is 3600rpm and the velocity of the vehicle is 55km/hr.

 

 

 

Output plot and CVT Shaft Speed:

                  

 

BAJA CVTModel_cvtratio_rpm:

 

 In this model, a lookup table was taken instead of Signal Builder to provide different gear ratios data. The data in the Lookup table need to be imported to the Matlab workspace. While doing simulation data is retrieved from the workspace and provided to the CVT subsystem. The remaining are all same as the first CVT model.

 

Lookup Table data in the workspace:

Output results:

                              

 

 

BAJA CVTModel_dashboard_mapped: In this model brake input and throttle input are given through constant blocks instead of signal Builder by just turning the knobs. We can input any value and observe the vehicle behavior within less span of time. The output velocity is taken as input to the PS Lookup table which is connected in CVT Subsystem. Lookup table data also imported from the workspace which provides variable gear ratios to the CVT subsystem. The results are observed after doing the simulation. The dashboard is provided to this model to give variable input values for brake and throttle input. These blocks are given connection to the model by selecting the radio button under connection in the popup window of circular gauges.

 

 

 

 

 

 

             CVT subsystem Model for Dashboard_mapped Model

LooyUp Table Visualization:

 

 

Output Results:  The speed of an engine is shown in a dashboard as 2400rpm and the velocity of the vehicle body is 42km/hr. After 70 seconds the vehicle velocity reaches too high and remains constant.e., 41-42km/hr.

 

 

                

 

 

BAJA AVT Model_mapped: This is the same as the above model. The output velocity is mapped to the Cvt subsystem. The input value of the brake and throttle are taken as step blocks.

 

 

 

 

      

 

 

CVT Subsystem Model:  In this model, we have taken the physical signal Loop table which has shown the error that the data in vehicle_speed vector in the workspace should be either in ascending or descending order. After changing the vector grid data order, the simscape model has taken data from the workspace.

 

 

Cvt Ratio from PS LookUp table:

 

 

 

 

Output results: The velocity of the vehicle more than 60km/hr when compared to the previous model. Here the input throttle value is step value from 0.3 to 1 taken whereas in the previous model exact value of 0.3 was taken.

 

     

 

BAJA CVTModel_data: In this model, two signal builder blocks were taken. One for brake input and throttle input and the other one for CVT Ratio. No mapping has been done for this model. The performance of the vehicle model is observed after stimulation. Throttle value is given as step value from 0.3 to 1.

 

 

 

                   CVT subsystem Model

                

 

 

 

 Input Signal:

    

 

Output Results: After 60 seconds the vehicle speed is increasing slowly and reaches the maximum value of 60 to 65 km/hr in the timespan of 500 seconds

 

       

 

 

CONCLUSION:

 All the model results are reported and observations are described which explains how a CVT model behaves when different ways of inputs were given and shown different simscape model ways.