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Electric Motor Industry and Switched Reluctance Machines
Published in Berker Bilgin, James Weisheng Jiang, Ali Emadi, Switched Reluctance Motor Drives, 2019
The second type of hub motors is the direct drive or gearless hub motors. Since the planetary gear set is eliminated, these motors provide higher torque at low speed. The maximum speed of gearless hub motors is around 500 rpm. The planetary gear set is the primary source of noise; therefore, gearless hub motors can deliver quieter operation. On the other hand, they are usually heavier, and since they are located on the wheel, they position the weight towards the end of the bike. This may reduce the balance. Furthermore, since the motor weight is built into the wheel, this increases the unsprung mass. It means that the weight of the gearless hub motor cannot be sprung as a part of the frame [22]. Surface permanent magnet brushless DC motors with concentrated windings are the preferred choice for gearless hub motors. Figure 1.14 shows the picture of a commercial gearless hub motor from Crystallite. It is an exterior rotor machine, and the magnets are located on the inner surface of the rotor.
Automotive Architecture
Published in Patrick Hossay, Automotive Innovation, 2019
The typical suspension uses springs to absorb road bumps and accommodate vehicle movement. As you might remember from your middle school science class, any mechanical spring exhibits a tendency toward harmonic oscillation. That is to say, if you compress or stretch an elastic body, it will move to restore it’s original shape, but overshoot, and so be drawn back somewhat in the direction of the initial displacement, then rebound back, overshoot a bit less, and move back once again, and so on, defining a diminishing sinusoidal motion until it has used up its energy. If you like crazy carnival rides, this might be a fun way to ride in a car. But for the typical driver, bouncing down the road is not pleasant; and extreme wheel bounce tends to ruin handling and stability. So, we dampen the spring’s oscillation with the poorly named shock absorber. These shock absorbers don’t really absorb much shock, they dampen the springs’ oscillation to prevent an otherwise wavy ride. Typically composed of a cylinder filled with oil or gas, and a sliding piston that works against the fluid viscosity, they provide proportional resistance to movement. The greater the speed of the movement between car and wheel, the stronger the resistive force. These two features, a spring and a dampener, define the dynamics of the connection between the sprung mass above (the body, chassis, and drivetrain) and the unsprung mass below (wheels, tires and brakes). A key concern is to keep the unsprung mass as small as possible, as the larger the mass, the greater the upward force imposed on the suspension with every bump, and the more challenging it is to absorb.
Influence of in-wheel motors on the wheel shimmy of 4 WID electric vehicles
Published in Maksym Spiryagin, Timothy Gordon, Colin Cole, Tim McSweeney, The Dynamics of Vehicles on Roads and Tracks, 2018
Ning Zhang, Ying Xu, Gang Li, Xiaogao Li, Nan Chen
Fig. 3 is the bifurcation diagrams of the shimmy system in different moment of inertia. With the rise of the moment of inertia, the unstable area shrinks. Not only the unstable area changes, but the amplitude of the angle of the front wheel around the kingpin has changes. With the rise of the moment of inertia, the amplitude is bigger that means the rise of the moment of inertia caused the vehicle larger oscillation. It is obvious that a bigger unsprung mass increases the dynamic wheel load and consequently has influence on the vehicle stability and comfort. Therefore, the results of the bifurcation diagrams provided a guidance to choose suitable IWMs.
Road roughness estimation based on discrete Kalman filter with unknown input
Published in Vehicle System Dynamics, 2019
Sun-Woo Kang, Jung-Sik Kim, Gi-Woo Kim
The measurement equation can then be expressed as follows: where In Equation (19), is the suspension deflection, is the sprung mass acceleration, is the sprung mass displacement, and is the unsprung mass acceleration. The suspension deflection can be measured by a height sensor or wheel stroke sensor. The sprung mass and unsprung mass acceleration also can be measured by an accelerometer mounted on a vehicle body and wheel. However, the sprung mass displacement needs to be calculated by doubly integrating the acceleration signal because it is generally difficult to measure the sprung mass displacement. A high pass filter is used to remove the low frequency drift error occurred during the integration process [5]. In addition, since the bandwidth of the general suspension system ranges from 0.5 to 15 Hz, the high pass filter is designed to have a cut-off frequency of 0.5 Hz [25].
Enhancing rail infra durability through freight bogie design
Published in Vehicle System Dynamics, 2018
Martin Hiensch, Nico Burgelman, Wouter Hoeding, Mark Linders, Michaël Steenbergen, Arjen Zoeteman
Developments in bogie design are seen to also target the bogie mass for which a reduction can be achieved, for example, by the inboard bearing wheelset concept and hollow axles considerably reducing the unsprung mass together with a low weight bogie frame design. The effect of reducing the unsprung mass of the bogies on track degradation is investigated by examining the forces between wheel and rail in lateral and vertical direction. Reduction of the unsprung mass is implemented in the vehicle model by reducing the mass per wheelset with 400 kg; additionally the mass per bogie frame is reduced with 200 kg. This results in a mass reduction of 1000 kg for each bogie (approx. 20% reduction) and implies 2000 kg of extra freight. To illustrate the effect of the individual changes in mass of bogie frame (sprung) and wheelset (unsprung), simulations have been carried out for the following three configurations (all variants retaining 22.5 tons axle load): (1) Reference Y25, (2) mass of each wheelset reduced with 400 kg (Ws-400) and bogie frame reduced with 200 kg (b-200) adding 2000 kg of extra freight to the wagon and (3) mass of each wheelset reduced with 400 kg (Ws-400) adding 1600 kg of extra freight.
Contributions of vehicle dynamics to the energy efficient operation of road and rail vehicles
Published in Vehicle System Dynamics, 2021
Jenny Jerrelind, Paul Allen, Patrick Gruber, Mats Berg, Lars Drugge
The possible reduction in unsprung mass is small compared to the vehicle mass, but can reduce the dynamic wheel-rail forces and associated damage significantly. Two wheels connected by a common axle typically have a mass of around 1 t, but unsprung mass is further increased when considering axle boxes, brake discs and traction gear. An example of making the axle lighter is given by Mistry and Johnson [35]. In this publication two approaches were considered. One dealt with a hollow steel axle design resulting in more than halving the axle mass. The other approach continued with a hollow axle design but replaced steel with different composite materials. Mass savings achieved were cited as being more than 80% compared to a solid steel axle.