Project

                                                           Simulink for Mechanical & Electrical Engineers

 

Aim: - To study and analyze the BAJA All-Terrain Vehicle (ATV) Model and to perform system-level simulation by using Simulink.

Objective: -

• To carry out a system-level simulation of an all-Terrain Vehicle and to prepare a technical report explaining the model properties and comments on the results.

 

Description: -

               

               

An all-terrain vehicle is also known as quad, quad bike, three-wheeler or four-wheeler is defined by the American National Standards Institute (ANSI) as a vehicle that travels on low pressure tires, with a seat that is straddled by the operator along with the handle bars or with a steering control. ATV can handle a wider variety of terrain like hilly, rocky, bumpy, lose gravel, muddy, mountainous areas, etc. It is specially designed for off-road usage.

Continuously Variable Transmission (CVT) – It is an automatic transmission that can change seamlessly through a continuous range of gear ratios. CVT transmission systems are also known as single-speed, shiftless and stepless transmissions. A CVT achieves the infinite gear ratio flexibility by using two opposing cone-shaped pulleys with chain or belt that runs between. One cone is connected to the engine output shaft, while the other cone directs power to the driveshaft and drive the wheels. Gear ratios change as the pulleys move closer and further apart, causing the chain or belt to move up and down the two cone’s sides. This movement increases or decreases the diameter of the chain or belt, which alerts the gear ratio based on the power needed. CVT are more efficient than standard automatic transmissions and are commonly utilized in hybrid powertrains. Due to variable characteristics, a CVT can typically find the proper gear ratio much faster than an automatic transmission at virtually every speed ranging from off the line to highway passing. The continuous variable transmission are simpler and more adaptable than traditional transmissions, offering impressive fuel economy and seamless performance through varying driving conditions.

Simulation is carried out for 4-different cases, they are;

• Case:1   Simulink Model for BAJA ATV with CVT (Without Dashboard)

• Case:2   Simulink Model for BAJA ATV with CVT (With Dashboard)

• Case:3   Simulink Model for BAJA ATV with CVT using Lookup Table (Without Dashboard)

• Case:4   Simulink Model for BAJA ATV with CVT using Lookup Table (With Dashboard)

 

 

Case:1   Simulink Model for BAJA ATV with CVT (Without Dashboard)

 

 

The above model is a BAJA ATV Model without dashboard.

• The first block is the signal builder block, which is used to create and generate interchangeable group of signals whose wave forms are linear. Here both Brake Input and Throttle Input are specified and considered as inputs.

• The Throttle Input in the signal builder is connected to the Generic Engine block by means of a Simulink-PS Converter. i.e., the throttle input signal is connected to the ‘T’ terminal of the Generic Engine block.
• Generic Engine is nothing but the internal combustion engine with throttle and rotational inertia and time lag. The Generic Engine Block represents a general internal combustion engine.

• From the above block, the input signal ‘T’ lies between zero and one and specifies the torque demanded from the engine as a fraction of maximum possible torque. The connections ‘F’ and ‘B’ are the mechanical rotational conserving ports associated with the engine crankshaft and engine block respectively. Likewise, the connections ‘P’ and ‘FC’ are physical signal output ports through which engine power and fuel consumption rate are reported.
• As shown in the main model, port ‘B’ is connected to the solver configuration and the mechanical reference. The port ‘F’ of the Generic Engine Block is connected to the port ‘F’ of the Engine Sensor Block.
• The ports of Generic Engine Block are;

‘T’ – Normalized engine throttle level (input) - Normalized engine throttle level (physical signal). Engine torque demand as a fraction               of maximum possible torque.

‘P’- Instantaneous engine power (output) – Instantaneous engine power (physical signal). Its nothing but the power produced by the engine.

‘FC’ – Fuel consumption rate (output) - Fuel Consumption rate (physical signal). The fuel consumed by the engine is given by this term.

‘B’- Engine Block (conserving-Mechanical Rotational) – Mechanical rotational conserving port associated with the engine block. The engine block is the physical body that contains piston cylinders.

‘F’- Engine crankshaft (conserving-Mechanical Rotational) - Mechanical rotational conserving port associated with the engine crankshaft.

 

 

• The port ‘F’ of the Generic Engine Block is connected to the port ‘F’ of the Engine Sensor Block.

• A subsystem block is created where the the input signal signal is ‘F’ and the output signal of the block is ‘B’. The below images shows the complete subsystem that is created inside a Engine Sensor Block.

 

 

‘W’- Angular velocity (physical signal)

‘A’- Angular Displacement

‘R’- Rod (positive probe) - conserving-Mechanical Rotational

‘C’- Rod (reference probe) - conserving-Mechanical Rotational

• Inside the subsystem, the Connection Port Block is used to transfer a physical connection or signal across the subsystem boundaries i.e., the signal of port-F from Generic engine block is transferred to the subsystem boundary of Engine Sensor Block. So Port-1 is the input signal of the engine sensor block and Port-2 is the output signal of the engine sensor block.
• An Ideal Rotational Motion Sensor Block is used to measure between two mechanical rotational nodes into a control logic signal that is proportional to the angular velocity or the angle. The ports ‘R’ and ‘C’ are mechanical rotational conserving ports and connections ‘W’ and ‘A’ are the physical output signals for velocity and angular displacement.

• The Port-C is connected to the Mechanical Rotational Reference, Port-W is connected to the scope i.e., Engine RPM and Port-A is connected to PS Terminator. This PS Terminator block is used to cap physical signal output ports that do not connect to other blocks.
• The output of the Engine Sensor Block is connected to the CVT block. And also, to this a signal builder is connected in which the gear changing parameters are set in it.

CVT   Subsystem:

• The output of the Engine Sensor Block (Port-B) is connected to the Physical Modeling Connection Port (PMC_PORT) in the CVT Subsystem i.e. (Port-B).
• This is then connected to the Input Shaft Inertia i.e. (Inertia Block). This block represents an ideal mechanical rotational inertia.
• As shown in the above subsystem, Ideal Rotational Motion Sensor Block is connected to the signal that is coming from Inertia block to Port-R. For Ideal Rotational Motion Sensor Block Port-C is connected to Mechanical Rotational Reference, Port-W is connected to the go to block and Port-A is connected to PS Terminator.
• The signal from port-B is further connected to Variable Ratio Gear (Variable Ratio Transmission block). This block represents a variable ratio gearbox such as implemented by mechanical belt CVT, electric, or hydraulic transmissions. The variable ratio transmission block consists of connections B(base) and F(follower), which are mechanical rotational conserving ports.

• Here the we specify the direction of rotation of the output shaft. Port-R is connected to the Inport Block i.e., it provides an input port for a subsystem or a model. Now the output of Variable Ratio Gearbox with port-F is connected to the follower(F).
• One signal is connected to Ideal Rotational Motion Sensor where all the parameters same whereas the value in the go to block is considered as secondary.
• Now the output of the CVT block is connected to a Simple Gear Block. Here it represents a fixed ratio gear or a gearbox and also, we specify the follower to base teeth ratio and the direction of rotation of the output shaft.

• The output of Simple Gear Block is then connected to the Vehicle Body Block (it is a subsystem)

   Vehicle Body Subsystem:

• The above model shows the vehicle is the output from the gearbox is connected to the rear axle. For this inertia is added in order to simulate axel inertia. Now the show brake (Port-S) conserving port is then connected to the axel.
• The same axel now connects the both rear tires while both the front tyres are free to rotate on a particular rotational free end.
• All the H-Ports are connected together and this is connected to the vehicle at Port-H. And also the rear N-Ports of the rear tyres are connected together and connected to the vehicle body at port-Nr (output). While the front are connected to the port-Nf (output).
• In order to provide the wind velocity and inclination, a PS Constant block is used to declare the constants.
• Finally, all the necessary output parameters that are given with go to block are connected to the output block and also as mentioned , the primary value and the secondary value are also connected to the scope block i.e. CVT Shaft Speed. Engine Torque vs Speed curve  is also set to plot.

• With this the complete model is setup for this case.

 

Results: -

Engine Torque vs Speed Curve:

 

• The speed and torque are the inputs from the MATLAB Workspace window, which is linked to the ‘Generic Engine Block’ in order to generate the output RPM. This parameter for torque vs Engine speed is set as default input to the engine.

 

Engine Speed vs Time:

The engine rpm i.e., speed of the engine is observed using Engine sensor. The engine rpm is generated based on the throttle, speed and the torque inputs as specified.

 

 

CVT shaft speed vs Time:

• Continuously Variable Transmission (CVT) is an automatic transmission that can change seamlessly through a continuous range of gear ratios.
• The below plot shows how the engine speeds are controlled by various CVT gear ratios.
• The plot shows two different curves i.e., ‘CVT Primary RPM’ and ‘CVT Secondary RPM’. Here the CVT Primary RPM represents the initial speed that is observed in the CVT and CVT Secondary RPM represents the fluctuation as per the gear ratios.  

 

 

Vehicle speed w.r.to. Throttle and brake:

• As per the initial conditions its observed that the brake is not applied in the complete drive as the plot clear shows that it lies on zero.
• In this case the throttle is also maintained to 0.5 as shown in the second plot. Also, till the end of the drive cycle the throttle is remained constant.
• It is also observed that, with increase in the throttle position the vehicle speed also increases.
• As the brake input value is maintained to zero, there is no effect on the velocity.

Throttle and Break Output:

 

Case:2   Simulink Model for BAJA ATV with CVT (With Dashboard)

 

 

• In this case the model includes the dashboard as shown in the above image.
• The dashboard is specified with the throttle input and the brake input. Signal builder is replaced with dashboard for providing the input parameters.
• Here in this case all the blocks, subsystems etc., are similar to the case-1. Here only the dashboard is included by removing the signal builder.
• The perspective of using the dashboard concept is to study analyze the result by varying the input of brake and the throttle which represents the velocity and speed of the engine.
• The dashboard is controlled through a knob which can be varied i.e., changing the parameters of Brake Input and Throttle input.
• The dashboard for input parameters is shown below;

• The input controls are varied by using the knob that is provided. This are connected to the blocks i.e., Brake input and Throttle input. On varying the knob, the changes in the values are observed. Here the run time is not specified as the inputs are user defined by controlling the knob.

 

Results: -

Engine Torque vs Speed Curve:

• The speed and torque are the inputs from the MATLAB Workspace window, which is linked to the ‘Generic Engine Block’ in order to generate the output RPM. This parameter for torque vs Engine speed is set as default input to the engine.

Engine Speed vs Time:

• The engine rpm i.e., speed of the engine is observed using Engine sensor.
• The engine speed is achieved based on the throttle, speed and the torque inputs as specified. Here Run time is maintained infinity as we give the throttle and brake input through varying the knobs.
• Based the fluctuations in the input parameters, the below plot shows the engine speed or velocity.

 

 

CVT shaft speed vs Time:

• Continuously Variable Transmission (CVT) is an automatic transmission that can change seamlessly through a continuous range of gear ratios. The plot shows two different curves i.e., ‘CVT Primary RPM’ and ‘CVT Secondary RPM’. Here the CVT Primary RPM represents the initial speed that is observed in the CVT and CVT Secondary RPM represents the fluctuation as per the gear ratios.
• The below plot describes how the engine speeds are controlled by various CVT gear ratios. Both primary and secondary follow the same trend.

 

Vehicle speed w.r.to. Throttle and brake:

• By providing the initial conditions its observed that the brake is not applied in the complete drive as the plot clear shows that it lies on zero.
• It is also observed that, with increase in the throttle position the vehicle speed also increases. The constant speed is observed in the velocity path line as there are no changes in throttle or brake at that point.
• Here the run time is not specified because throttle and break are controlled by the user.

 

 

Case:3   Simulink Model for BAJA ATV with CVT using Lookup Table (Without Dashboard)

 

• From the above model it is observed that the workflow process is same as it is in case-1, but instead of Signal Builder Block, the ‘STEP BLOCK’ is used for both input parameters brake input and throttle input.

• The CVT Sub system is the same as the previous cases, but for CVT Gear Ratio the Lookup Table is used.

• The file – ‘Lookuptable_data.mat’ is loaded in the workspace in order to declare the parameters.

• In this case, the vehicle speed is given as the feedback to the feedback to the CVT Ratio lookup table. The below image represents the Lookup Table Visualization;

 

 

Results: -

Engine Torque vs Speed Curve:

• The speed and torque are the inputs from the MATLAB Workspace window, which is linked to the ‘Generic Engine Block’ in order to generate the output RPM. This parameter for torque vs Engine speed is set as default input to the engine.

 

CVT ratio w.r.to Time:

• Cvt ratios are specified using the lookup table in this case. It is a physical signal converter whose Input-output relation is specified by look up table. The following image shows the Lookup table visualization at the output end.

 

Engine Speed vs Time:

• The engine rpm i.e., speed of the engine is observed using Engine sensor. The engine rpm is generated based on the throttle, speed and the torque inputs as specified.

 

CVT shaft speed vs Time:

• Continuously Variable Transmission (CVT) is an automatic transmission that can change seamlessly through a continuous range of gear ratios.
• The below plot shows how the engine speeds are controlled by various CVT gear ratios.
• The plot shows two different curves i.e., ‘CVT Primary RPM’ and ‘CVT Secondary RPM’. Here the CVT Primary RPM represents the initial speed that is observed in the CVT and CVT Secondary RPM represents the fluctuation as per the gear ratios.  

 

Vehicle speed w.r.to. Throttle and brake:

• The final vehicle speed is obtained and completely dependent on the parameters like throttle, gear ratios change and the braking conditions. The plot of vehicle speed w.r.to time is shown below.
• As per the initial conditions its observed that the brake is not applied in the complete drive as the plot clear shows that it lies on zero.
• In this case the throttle is also maintained as per the initial conditions i.e., step time =20, initial value=0.3, Final value=1 and Sample Time=0. This is shown in second plot. Initially it varies as specified and then later it remains constant.
• It is also observed that, with increase in the throttle position the vehicle speed also increases.
• As the brake input value is maintained to zero, there is no effect on the velocity.

 

Throttle and Break Output:

 

 

Case:4   Simulink Model for BAJA ATV with CVT using Lookup Table (With Dashboard)

 

• In this case the model includes the dashboard as shown in the above image.
• The dashboard is specified with the throttle input and the brake input.
• Here in this case all the blocks, subsystems etc., are similar to the case-3. Here only the dashboard is included.

 

• The dashboard for input parameters is shown below;

• The dashboard is controlled through a knob which can be varied i.e., changing the parameters of Brake Input and Throttle input.
• In this case, the vehicle speed is given as the feedback to the feedback to the CVT Ratio lookup table. The below image represents the Lookup Table Visualization.

• A lookup table is used to look up a secondary value based on a primary value. It uses an array of data to map input values to the output values.
• By giving input values, Simulink performs a lookup operation to retrieve the corresponding output values from the table.

 

Results: -

Engine Torque vs Speed Curve:

• The speed and torque are the inputs from the MATLAB Workspace window, which is linked to the ‘Generic Engine Block’ in order to generate the output RPM. This parameter for torque vs Engine speed is set as default input to the engine.

 

Engine Speed vs Time:

• The engine rpm i.e., speed of the engine is observed using Engine sensor. The engine rpm is generated based on the throttle, speed and the torque inputs as specified.

 

CVT shaft speed vs Time:

• Continuously Variable Transmission (CVT) is an automatic transmission that can change seamlessly through a continuous range of gear ratios.
• The below plot shows how the engine speeds are controlled by various CVT gear ratios.
• The plot shows two different curves i.e., ‘CVT Primary RPM’ and ‘CVT Secondary RPM’. Here the CVT Primary RPM represents the initial speed that is observed in the CVT and CVT Secondary RPM represents the fluctuation as per the gear ratios.
• From the below plot it is observed that the CVT secondary rpm plot and the velocity of the vehicle behaves the same as the secondary pulley is connected to the vehicle output.

 

Vehicle speed w.r.to. Throttle and brake:

• The final vehicle speed is obtained and completely dependent on the parameters like throttle, gear ratios change and the braking conditions. The plot of vehicle speed w.r.to time is shown below.
• It is also observed that with varying the throttle position continuously the velocity changes as per the given input. It reaches to maximum velocity is around 60Kmph.
• As per the initial conditions its observed that the brake is not applied in the complete drive as the plot clear shows that it lies on zero.

Conclusion: -

• The system level simulation of an BAJA All-Terrain Vehicle (ATV) is carried out for different cases and for all the cases the necessary output data is plotted by varying the given input data.
• Therefore all the cases are analyzed and the outputs are recorded.