The basic principle behind a vehicle equipped with in wheel motors electric is simple. The internal combustion engine normally found under the hood is simply not necessary. It is replaced with at least two motors located in the hub of the wheels. These wheels contain not only the braking components but also all of the functionality that was formally performed by the engine transmission clutch suspension and other related parts. Although the concept is relatively simple in theory and will motor pose several questions about performance, function, and efficiency.
How does it work
In recent years, we have seen some vehicle developers moving toward powertrain configurations where the motor is mounted inside the wheel, an inward motor system.
We must admit there is an impressive amount of new space available when the electric motors are integrated into the wheels. These are called hub-motors or in wheel motors with certain benefits but also create some challenges. In wheel motors aren’t new at the beginning of the 20th century Ferdinand Porsche’s first hybrid vehicle used hub-mounted electric motors on each wheel these motors power the wheel directly there’s no need for a gearbox or drive shaft.
When using a reduction gearbox the speed is reduced and the torque is multiplied but with an inward motor, there is no reduction. Wheel speed is equal to motor speed the requires torque and power need to be delivered in a direct drive mode. In wheel motors are directly exposed to dust salt water and other fluids but also to vibrations and shocks which shortens their life expectancy. That’s one of the main reasons for eventually deciding to ditch the inward motors concepts that they were working on for the new electric f-150 in 2008. The four-wheel motors are also known as quad motor drives. These four motors deliver instant power and independently adjust torque at each wheel for precise traction control in all conditions. Controlling power at the individual will enables torque vectoring. Quad motors offer substantially better torque control than locking differentials while also being instantly adjustable for on-road performance.
Design of in wheel motors
Producing a vehicle that uses in will electric motors is a process that’s a lot more complex than just tearing out the engine works and then cramming electric motors into the unused space inside the wheel. This type of electric motor is designed to work on hybrid vehicles. Full battery operated vehicles and even fuel cell powered electric vehicles. The amount of power generated by these in wheel motors can vary depending on the manufacturer and the size of the motor. The electric motor is installed inside the wheel and provides power to it directly without the need for any transmission.
The idea of installing the motor inside the wheel rim in an EV is the right choice. In this way, it can be ensured that the full output power of the motor is available at the wheel without any mechanical transmission losses. The number of in wheel motors a vehicle uses can be adjusted to meet the vehicle requirements for instance in most cases two motors will supply sufficient power. If the EV is equipped with two motors in the front will axle and thus the vehicle is a front wheel drive or in the rear will axle and the vehicle is a rear wheel drive. However, if you are talking about an all-wheel drive vehicle either an off-road truck or a performance car that would require to be equipped with an electric motor at each wheel.
Pure electric vehicles with in wheel min wheel have a simpler design for both chassis and drivetrain and they do not require any driveshaft differential and transmission.
In wheel motor power
The combination of several in wheel motors can put out more than 600 horsepower and they can receive their energy while braking.
Do these in wheel electric motors provide enough torque for every application?
After all, torque plays an important role in any automobile’s response time and performance. In a vehicle equipped with in wheel electric motors, there’s plenty of torque available almost instantly electric motors produce a high amount of torque and since that force is transmitted directly to the wheel very little is lost in the transfer. Each will can be equipped with sensors to determine how much torque is required at any given time.
Similar systems exist in cars on the road now but the response times are slightly slower due to the number of components involved and the more complex electrical communication pathways eliminating the engine make it possible to add design and structural enhancements to a vehicle. Today, in-will electric motor system testing has been conducted by many automakers and technology companies, including the Ventura corporation of Monaco, for use in its voltage concept vehicle, but questions of reliability, durability, and safety are difficult to report without widespread usage of the system.
How in wheel motor EV is different from other cars?
For traditional IC engine vehicles, the drivetrain system consists of the conventional mechanical systems the engine, transmission, exhaust system, drive shaft, and differential. In a conventional EV, the engine is replaced by an electric motor with an inverter and a set of batteries installed at the back. In the case of EVs that use in will motors, all the mechanical subsystems of the powertrain are eliminated and replaced with direct drive and wheel motors that do not need any drive shaft as they are connected to wheels. The only remaining system in this type of EV is the conventional suspension inward motors that can be used to deliver the torque vectoring strategies present in many high-performance vehicles.
What is torque vectoring?
Torque vectoring is the technology that distributes an engine’s power across the left and right sides of the car. It is commonly employed in differential to vary the torque to each half shaft with an electronic system with torque vectoring one side of the wheel on the axle can go faster or slower than the other. Torque vectoring or perhaps more accurately termed torque biasing is becoming more common on high-performance vehicles as a way to deliver improved cornering performance.
Torque vectoring aims to improve steering response and handling through the distribution of torque between the wheels. By controlling the power across the axle more effectively the car can corner with more grip and turn into a bend quicker. This is achieved by adding your moment onto the vehicle via active differential brakes or other mechanical solutions there are plenty of ways to do torque vectoring.
The most common is brake-based where the inside wall is slowed slightly by applying the brakes to one side of the vehicle but not the other. That can be effective but it means you are squandering power torque is being sent to the wheel but you are artificially reducing its efficiency better is a torque vectoring differential that has the same outcome slowing the inside wheel but it does so by actually reducing torque to that wheel. At the same time, the torque is increased to the outside wheel meaning you are not wasting power overall. When you get to an EV things can be even more interesting than you can have an electric motor dedicated to each wheel each independently controlled. It can be faster and more responsive too since it adjusts torque electronically by how much power goes to each motor rather than mechanically.
The efficiency of In wheel motors
In wheel, motors will always suffer more from no load losses and part load losses because the motors can’t be decoupled from the wheels. There is a trend of mounting more motors in a vehicle and what we see for what we see for example with the Porsche take-in is that the rear motors are decoupled from the wheel when crushing at highway speed to optimize the efficiency of the powertrain. This is very difficult to implement with in wheel motors. They always rotate with the wheels even when not used actively. Some companies claim that the efficiency within will motors is higher because there is no gearbox. Although a gearbox does always introduce a bit of inefficiency the one or two-speed gearboxes that are typically used for EVs are much more efficient than the complex multi-stage transmissions seen in combustion engine powertrains. We are looking at one or maybe two percent efficiency loss in the gearbox This loss in efficiency is overcompensated by the fact that due to the gearbox. The electric motor can run in its most efficient operating area increasing vehicle range when compared to a direct drive system depending on the use case and driving cycle. Some in wheel motor designs offer regenerative braking as well which means the system captures some of its kinetic energy while braking and sends it back to charge the battery. Some hybrids such as the TOYOTA PRIUS and TESLA ROADSTER already incorporate this regenerative braking technology which provides the automobiles with a longer driving range.
One of the greatest advantages of in wheel electric motors is the fact that the power goes straight from the motor directly to the wheel. Reducing the distance the power travels increases the efficiency of the motor. For instance, in city driving conditions an internal combustion engine may only run at 20 efficiencies meaning that most of its energy is lost or wasted via the mechanical methods employed to get the power to the wheels. An electric motor in the same environment is said to operate at about 90% efficiency.
Is this the future of electric vehicles?
Porsche engineering has developed a torque control system for a four-motor electric vehicle drivetrain that lets electric SUVs handle with the agility of a sports car in even the most difficult conditions because of the much faster responsiveness of an electric motor as compared to an IC engine EV traction control systems can respond much more quickly in an electric vehicle the torque is purely electronically controlled which works considerably faster than mechanical clutches. Every mile-second intelligent software distributes the forces in such a way that the vehicle always behaves neutrally but Porsche’s solution is not just all-wheel drive it utilizes four separate motors one controlling each wheel.
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There are advantages and disadvantages of multiple motors. More motors increase cost and complexity but eliminate the need for a drive shaft and give more control. Motors can also increase the sprung weight which can have some negative effects on handling and ride quality. According to Chris Hilton CTO of protein electric in the will, motors improve handling because of each will can be finally controlled. They also lower the overall center of gravity and help to reduce weight and optimize weight distribution in the vehicle. Also because inward motors are located in the wheel there are minimal losses in transmission of the torque to the road as they are more efficient. this means greater vehicle range or the same range from a smaller battery.
Another firm working on veal motors is Japan’s NIDEK which announced its prototype in 2019. According to NIDEK the motor has a long list of advantages for example it produces less noise due to fewer moving parts but perhaps the biggest advantage is space. Cars that use in wheel motors don’t need a motor compartment also with the elimination of the drive shafts the wheel can rotate freely for example it becomes possible to rotate the wheels 90 degrees and drive to the left or the right or even rotate in place instead of just driving forward or backward. This adds another dimension to how the car can move around and makes it easy to navigate tight spaces.
RIVIAN R1T truck:
The new R1T features one engine for each wheel. This quad motor drivetrain enables the RIVIAN truck to handle like a sports SEDAN on road and four-by-four off-road with ease. No other production truck offers this feature the R1 TEV will leave its competitors in the dust. In the straight line, the RIVEN R1T is one of the world’s fastest trucks.
The RIVIAN truck’s quad motor drive system can put an incredible 800 horsepower to the wheels. On the proper tires and R1T can accelerate from zero to sixty miles per hour in 3 seconds. This reportedly makes the R1T the fastest truck in the world. The RIVIAN R1T electric truck is not the cheapest option on the market but with quad motor drive and algorithms to distribute torque instantly both on road and off it is the most versatile electric truck on the market. The RIVIAN R1T will leave an electric super truck with six-figure price tags struggling to catch up.
Advantages of in wheel motors:
- In wheel motors are easy to install and replace.
- They add flexibility as they can be used to power rear or front-wheel drive as well as all-wheel drive vehicles without much change in the drivetrain.
- They are compact in size.
- In wheel motors provide high efficiency due to the lack of mechanical losses from the transmission, differential, and drive shafts and make the car run quieter.
- With electronic motor control, it is possible to fine-tune and will motor torque, Rpm, and even direction of spin.
- This means features such as ABS traction control and even cruise control could be handled more efficiently.
Disadvantages of in wheel motors:
The major challenge in wheel motors face is the issue of un-sprung weight.
Un-sprung weight is the mass of all components including the frame motor passengers and body that are not supported by a car’s suspension.
Un-sprung weight includes wheels tires and brakes and it travels up and down over any bumps and potholes as it tires to follow the contours of the road and with the hub motors being part of the vehicle’s un-sprung weight they will feel the impact of every pothole, bump and high speed turn.
They will be exposed to road dirt, mud, dust water and road salt that can be reduced the longevity of the motors.
Inwards motors are expensive than a single mount on rear axle.