2009/5/10 Michel Jullian <[email protected]>: > 2009/5/10, Hoyt A. Stearns Jr. <[email protected]>: >> You're right of course, Kyle, except the trend will be that vehicle >> suspensions >> will be active and computer controlled and the energy recovery will be a >> natural >> result of the motor drive circuitry. > > That's what I would have answered if you hadn't beaten me to it!
Found this 2009 PhD thesis (Mechanical Engineering) on the subject: http://uwspace.uwaterloo.ca/bitstream/10012/4375/1/Babak_Ebrahimi_PhD_Thesis.pdf It contains a detailed review of research in this area: <<1.3.4 Electromagnetic Dampers In conventional hydraulic suspension systems, shock absorbers convert the mechanical energy of the vibration into heat energy, so this mechanical energy is dissipated (Suda et al., 1996). Segal et al. (1982) have demonstrated that roughly 200 watts of power are dissipated in an ordinary sedan traversing a poor road at 13.4 m/s; hence, suspension systems have the potential for energy regeneration. Using electromagnetic dampers (composed of electromechanical elements), the kinetic energy of vehicle body vibration can be regenerated as useful electrical energy. The electromagnetic dampers (as actuators) have the potential to be used in active suspension systems. Some authors have proposed self-powered active control systems by means of regenerative shock absorbers (Wendel et al., 1991). This new generation of shock absorbers is expected to be available for practical use in the near future. Karnopp (1989) has devised a new electromechanical damper for vehicle applications, consisting of copper wires and PMs. He has proven that for oscillation frequencies, typically expected in road vehicle suspensions, electro-dynamic variable shock absorbers are feasible. Suda et al. (1969) have used a rotating DC motor to convert vibrational energy to electrical energy. They have explained some trade-offs involved during the design process; for 16 example, there is a trade-off between the energy regeneration efficiency and the damping coefficient, which depends on DC machine internal and external resistance. They also used two linear DC motors, one in the primary suspension called “regenerative damper” which regenerates the vibration energy and stores it in the condenser, and the second linear DC motor in the secondary suspension system, which uses this energy to attain active control (Suda et al., 1998). Also, Suda (2004) has proposed another electromagnetic damper, as shown in Fig. 1-7, using DC motor, planetary gears, and a ball screw mechanism to convert the transverse motion of the vibration between the car body and wheels into the rotating motion of the DC motor. Arsem (1971) has proposed an electric shock absorber for automobile suspension systems. It converts the mechanical energy to electricity for charging the battery. The spiral screw causes the conversion of the linear motion to the rotary motion such that the screw moves up and down, the rotor starts to rotate, and an electric current is generated in the stator. Murty et al. (1989) have disclosed an electric variable damper for vehicle suspension systems, converting vertical suspension motion into rotary motion via a ball screw mechanism. To convert the three-phase alternator output to a single DC current, a rectifier bridge is used. The reported device dissipates the vibration energy as heat through a variable load resistance and does not recover the energy. Fig. 1-7 Proposed electromagnetic damper by Suda et al. (2004). Merritt et al. (1989) have proposed a linear electrical generator with a reciprocating armature with rectangular PMs, which are coupled to a source of relative motion. The device does not appear to fully utilize the magnetic field, generated by the PMs, since the generator uses only a single magnetic pole-coil interaction, which reduces the device’s efficiency. Konotchick (1994) has proposed several designs of linear electric power generators, consisting of a cylindrical assembly of rare earth magnets (NdFeB) and coils, positioned to move reciprocally relative to each other. The device is more appropriate for relatively large amplitude motions such as wave energy generation. To maximize the radial magnetic flux density in a linear generator that acts as a shock absorber, Goldner and Zerigian 17 (2005) have proposed a new assembly of magnet and coil winding arrays. The damper does not appear to be controlled actively, and so ride comfort and road-handling are sacrificed. Recently, Bose Corporation (maker of famous Bose speakers) has proposed an electromagnetic active suspension system for automobiles. The Bose active suspension system, composed of an electromagnetic motor as the actuator unit and a power amplifier, delivers electrical power to the motor in response to signals from the control unit. However, no data is available on the performance of these dampers. Fig. 1-8 Michelin active wheel with an active suspension system (Kendall, 2008). The Michelin Company also unveiled its electric drive system in late 2008. Fig. 1-8 depicts the Michelin novel active wheel incorporates an active suspension system. Their proposed system integrates a drive motor with electrical active suspension components. The principal component is a compact electric motor rated at 30 kW continuous output. A second motor provides power for the active suspension system, fitted vertically across the diameter of the wheel (Kendall, 2008). Michelin has claimed that the suspension system response time is 3 ms. With propulsion and suspension components fitted in the wheel, it would free up space in the front of the car that could result in better impact energy absorption, better interior packaging, and vehicle weight reduction. Gupta et al. (2007) described the manufacturing and implementation of two electromagnetic shock absorbers (one based on a linear motor and the other one based on a rotary dc motor) for a small allterrain vehicle (ATV). Similar to the design proposed by Goldner and Zerigian (2005), their proposed linear shock absorber is composed of two concentric coil rings moving relative to the two concentric magnet rings. 18 Finally, the most recent research in using the electromagnetic damper concept is done by Allen (2008). He presented the design, fabrication, and testing of an active suspension on a quarter-car system, using a tubular linear motor with various control algorithms. His master thesis is on developing control algorithms for the linear motor in the suspension system to minimize the transmitted acceleration to the sprung-mass.>> Detailed refs at the end of the thesis. Michelin's Active Wheel system makes most sense to me, not just because it's French, but because it looks like an elegant integrated solution for EVs. It's supposed to hit the road as soon as next year, the first cars using it will be the Heuliez Will and the Venturi Volage : http://reviews.cnet.com/8301-13746_7-10110393-48.html <<Issues with battery tech aside, electric motors allow for the creation of much simpler vehicles, without the need for exhausts, cooling systems, or complex lubrication schemes. The next logical step for electric vehicles is to move the electric motors into the wheel hubs themselves, replacing driveshafts, transmissions, and differentials with much lighter wires and switches. The primary problem with this configuration is the huge jump in unsprung weight that comes with mounting heavy electric motors inside of the wheels. Michelin Tires thinks it may be a step closer to solving this problem with its Active Wheel technology, unveiled at the 2008 Paris Motor Show. [...] The Heuliez Will--a prototype based on the Opel Agila--has been built in a partnership between Michelin, coachbuilder Heuliez, and the telecommunications company Orange. This front wheel drive prototype features an unsprung weight of 77 pounds per wheel on the front axle and 53 pounds per wheel on the rear axle (thanks to the omission of rear wheel motors). Michelin points out that the similarly sized Renault Clio features an unsprung weight of about 84 pounds at all axles, so the Active Wheel has already saved weight there. Offsetting the weight gained by the addition of the battery pack with the weight saved by the removal of the engine, fluids, differentials, transmission, and full fuel tank, and the final tally is a Heuliez Will that's 165 pounds lighter than the Opel Agila upon which it is based. The Heuliez Will also seats five, features two trunks--one in the back and one in the front where the engine used to live--and thanks to the contributions of Orange, features in-car high speed Internet and live traffic monitoring and navigation. The two in-wheel electric motors deliver 41 horsepower to the front axle (can you even still call it an axle?) and up to 82 horsepower for short sprints and merging. The Heuliez Will should hit 62 mph from a dead stop in 10 seconds and will have a max speed of 87 mph. Three lithium ion battery configurations are available offering ranges of 90, 185, and 250 miles. [...] The first batch of Heuliez Wills are testing now on the streets of France. Heuliez anticipates that they will be able to make the vehicle available in Europe, with the Active Wheel tech in place, for a limited release in 2010 and to the public by 2011 for an estimated price of 20,000 to 25,000 euros. [...] Those looking for a few more thrills, a few more kilowatts, and a much more exotic aesthetic should look for the Venturi Volage, which also features Michelin's Active Wheel system, but with a 0-60 time of about five seconds and a top speed of 93 mph. The Volage will see a limited production run--also in Europe--in 2012 for a yet unnamed price.>> Cheers, Michel
