Week-11 Challenge: Braking
- For a defined driving cycle, calculate the energy required for braking.
The driving cycle is a graphical representation of velocity concerning time. In MATLAB driving cycle is used for reference speed for vehicle design. If your vehicle is accelerating then the velocity of the vehicle is positive and the acceleration of the vehicle also positive. And if we apply a break on a vehicle then vehicle velocity is reducing then the acceleration of the vehicle is negative. When we apply break on the vehicle then it generates kinetic energy at wheel then that kinetic energy is calculated as
KE=0.5*M*V^2
Where M is the mass of the vehicle as 1100 kg
And V is difference between the velocity means the vehicle reduces its speed from 100 m/s to 0 m/s that speed id archiving in 10 sec
KE=0.5*1100*(100-0) = 55 KJ = 5.5 KW power
Kinetic energy is Require for breaking.
- Why electric motor can’t develop braking torque at a high speed similar to starting? How electric and mechanical brakes are coordinated?
Electric Motor: When the vehicle is operating at high speed then armature current and back EMF also at high. We remove the acceleration paddle force then the vehicle takes more time to stop the vehicle without breaking. If you want to stop the vehicle within the minimum time then breaking operation is required. If you apply breaking on a vehicle then supply break from load means wheel or motor. Then back EMF becomes more than supply voltage. Then armature current flow from load to source. Then armature current is reverse then torque depends on armature current. Then torque is also negative. Then the vehicle is operated with positive speed and negative torque then the vehicle is operated in a second quadrant. The braking depends on the speed of the motor.
If your speed of the vehicle is small then we can apply n=motor breaking. We consider the characteristics of the motor in which then speed is less than critical speed the torque applied on the vehicle is constant and high and the speed of the vehicle is less. If you apply regenerative breaking then torque has become is high. But at high-speed motor power is constant then speed is high and torque is low then we apply braking on the motor then it cannot operate here. Then we require mechanical braking at the high speed of the vehicle.
We conclude that when the vehicle is at low speed then we apply regenerative braking on the vehicle and the speed of the vehicle is high then we apply hybrid braking means we apply a combination of mechanical and Regenerative Braking.
When we apply mechanical breaking on the wheel means we apply a pedal then hydraulic pressure is created that pressure is applied on the wheel. The generation of pressure has two types
- Series breaking: two types of braking are applied on vehicles one is electric vehicle braking and mechanical braking. It applied one vehicle one after another.
- Parallel Breaking: when we apply to break parallel on vehicle both breaking is applied on the vehicle at a time to achieve desire braking on the vehicle.
3.Make a MATLAB program that plots the contour of given motor speed, torque, and efficiency values. Attach the code as a .m file attach a screenshot of all the plots.
