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Wheel hub motor

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Raleigh SC30 converted to an electric bicycle with an aftermarket electric conversion hub motor kit

A wheel hub motor, hub motor, or in-wheel motor is a motor that is incorporated into the hub of the wheel. Wheel-hub motors are commonly found on electric bicycles. Electric hub motors were well-received in early electric cars, but have not been commercially successful in modern production cars[1][2] because they negatively affect vehicle handling due to higher dynamic wheel load[3] and their placement makes them prone to damage.[2]

Bicycles

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Main article: Electric bicycle

Patents for electric bicycles with hub motors were granted as early as 1895.[4] Bicycle hub motors are simple, durable, and affordable compared to other designs, but less suitable for high speeds.[5] Hub motors rose in popularity over other designs in the late 2000s and 2010s.[6]

Automotive

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History

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1900 Lohner-Porsche "Chaise" battery electric vehicle with two front-wheel hub motors[7]
1900 Lohner–Porsche "Mixte" racecar with four wheel-hub motors[7]

Several electric, combustion, and steam powered in-wheel motor designs were patented in the 1880s and 1890s.[8] Among those who were awarded patents: Wellington Adams of St. Louis in 1884;[9] Edward Parkhurst of Woburn in 1890;[10] Albert Parcelle later in 1890;[11] Charles Theryc in 1896, who cites no transmission losses thanks to an absence of classic transmission rods from engines to wheels;[12] C F Goddard in 1896 who cites a piston hub motor for horseless carriages powered by expanding gas of some kind;[13] and W C Smith in 1897 who cites an explosive gas expansion motor inside a wheel hub that utilized cams on a track in the hub to transmit power to the wheel.[14]

An electric wheel hub motor car was raced by Ferdinand Porsche in 1897 in Vienna, Austria. He developed his first cars as electric cars with electric wheel hub motors that ran on batteries.[15] A racecar by Lohner–Porsche fitted with four wheel-hub motors debuted at the World Exhibition in Paris in 1900. Alongside it a commercial model was introduced, the Lohner–Porsche Chaise, with two front wheel-hub motors. It was well-received, and several models based on its design were produced by Lohner and other manufacturers until the 1920s.[16][7]

Design

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Hub motors may be implemented with direct-drive or planetary gears.[17] They rotate the wheel either through an axial, inrunner, or outrunner rotor design, with either brushed or brushless commutator design.[18]

Honda FCX Concept 2005 in-wheel motor with high-voltage wires in orange. Running high voltage outside the chassis can be avoided by using near-wheel motors, which have similar advantages to in-wheel motors.

Hub motors are attractive from a design standpoint because of their flexibility. They can be used for front-, rear-, or individual-wheel drive. They are compact and hence allow for more room for passengers, cargo, or other vehicle components. They allow for better weight distribution compared to a single motor, and they eliminate the need for many of the drive components in traditional vehicles like transmissions, differentials, and axles, which reduces wear and mechanical losses.[3][19] High-voltage in-wheel motors must be robust against damage to their high-voltage cables and components.[2]

Unsprung weight

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One disadvantage of a wheel hub motor is that the weight of the motor is not supported by the suspension's shock absorbers, adding to the vehicle's unsprung weight which adversely affects handling and ride quality. Despite this reduction in ride quality with electric hub motors, it is still better than the ride quality of equivalent combustion engine vehicles, but vehicle handling is still negatively affected due to higher dynamic wheel load.[3] Protean Electric and Lotus found that most negative effects of added unsprung mass could be eliminated by adding suspension damping, and that the ability to utilize accurate torque vectoring actually improved car's handling so much that the net effect of the whole arrangement was positive.[20]

Without being supported by the suspension's shock absorbers, in-wheel motors are themselves less shielded both from shocks and debris, reducing their durability. Some designs reduce unsprung weight by reducing the weight of the motor, for example by using a coreless design or Litz wire coil windings. These weight-saving designs may have a negative effect on motor durability.[19]

Near-wheel motors

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2011 Mercedes-Benz SLS AMG E-Cell prototype with four near-wheel motors[21] which share the advantages of in-wheel motors while avoiding issues of unsprung weight and wear

Similar to in-wheel motors, electric vehicles can be designed with near-wheel motors, sometimes called wheel-end motors. This design shares the same advantages as in-wheel motors while avoiding unsprung weight and wear issues, as the motors are near the wheels but inside the chassis, supported by the suspension. Near-wheel motors are less compact than in-wheel motors, but as of 2022 they are more reliable and more cost-effective,[22] they avoid the risks associated with out-of-chassis high-voltage components,[2] and they simplify vehicle design and assembly.[23]

American Axle has developed 100 kW and 150 kW wheel-end motors through a project funded by the United States Department of Energy for the commercialization of clean-energy low-cost wheel-end motors. Costs were lowered by integrating the motor, inverter, and gear reduction into a single unit, and by avoiding heavy rare earth elements.[24] The 100 kW 3-in-1 wheel-end drive unit has become commercially available in the REE Automotive vehicle product line.[23]

Concept cars

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An early modern concept car utilizing electric hub motors was the IZA, presented in at the IEEE conference in 1997, built with four 25 kW (34 hp) motors.[25]

Other concept cars presented at auto shows include: Chevrolet Sequel, 2005;[26] Mitsubishi MIEV, 2005;[27] Hi-Pa Drive Mini QED, 2006;[28] Honda FCX concept, 2005;[29] Citroën C-Métisse, 2006;[30] Protean Electric Ford F-150, 2008;[31] Heuliez WILL using the Michelin Active Wheel suspension, 2008;[32] Peugeot BB1, 2009;[33] Hiriko Fold, shown in 2012, a folding urban car with a maximum speed of 50 km/h (31 mph)[34][35] with a motor, steering actuators, suspension, and brake integrated into each wheel, controlled with a drive-by-wire system;[36] FlatFormer, a concept 6x6 autonomous truck chassis, shown in 2019;[37] various vehicles by Indigo Technologies since 2019;[2] and an Aptera Motors prototype in 2022.[38]

Concept cars that were announced without publicly presenting a physical model include: Siemens VDO eCorner concept, 2006;[39] and ZAP-X, 2007.[40]

  • Mini QED electric vehicle
    Mini QED electric vehicle
  • MAZ-7907 truck. Each wheel has its own electric motor
    MAZ-7907 truck. Each wheel has its own electric motor
  • Hiriko Fold with in-wheel motor, steering actuators, suspension, and braking, controlled by a drive-by-wire system
    Hiriko Fold with in-wheel motor, steering actuators, suspension, and braking, controlled by a drive-by-wire system

Production vehicles

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Production vehicles with in-wheel motors include:

  • Lohner–Porsche Chaise, Mixte, and others. Several models based on this design were produced by Lohner and other manufacturers in the early 1900s.[16][7]
  • Lightyear 0, briefly produced in 2022 before its manufacturer filed for bankruptcy.[41][42]
  • Lordstown Endurance, briefly produced in 2022 before its manufacturer filed for bankruptcy.[43]

Planned production vehicles include:

  • BMW plans producing by 2025 a vehicle with in-wheel motors developed by DeepDrive.[44]

See also

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References

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  1. ^ "Wheel Motors to Drive Dutch Buses". Technology Review. 23 March 2009.
  2. ^ a b c d e "A new type of engine for electric cars". The Economist. 11 July 2019. ISSN 0013-0613. Retrieved 31 August 2019.
  3. ^ a b c Vos, R.; Besselink, I. J. M.; Nijmeijer, H. (22–26 August 2010). Influence of in-wheel motors on the ride comfort of electric vehicles. Proceedings of the 10th International Symposium on Advanced Vehicle Control (AVEC10). Loughborough, United Kingdom. pp. 835–840.
  4. ^ (U.S. patent 552,271
  5. ^ Zachos, Elaina (16 June 2023). "Are electric bikes the future of green transportation?". National Geographic.
  6. ^ "Introduction to electric bikes: Everything you need to know". Cyclist.co.uk. 18 April 2017.
  7. ^ a b c d von Frankenberg, Richard (1961). Porsche – the Man and His Cars. Robert Bentley. p. 58.
  8. ^ Strohl, Daniel (12 February 2014). "Ferdinand Porsche, Joseph Ledwinka, and the invention of the electric hub motor". Hemmings.
  9. ^ U.S. patent 300,827
  10. ^ U.S. patent 422,149
  11. ^ U.S. patent 433,180
  12. ^ U.S. patent 572,036
  13. ^ U.S. patent 574,200
  14. ^ U.S. patent 593,248
  15. ^ "Ferdinand Porsche". Biography.com. 5 April 2021.
  16. ^ a b "Lohner". The World Guide to Automobile Manufacturers. Facts on File Publications. 1987. p. 294.
  17. ^ "Geared Hub Motors Vs Gearless Hub Motors". EbikeSchool.com. Retrieved 24 June 2023.
  18. ^ Christensen, Lowell (22 July 2014). "Designing In-Hub Brushless Motors". Machine Design.
  19. ^ a b Mraz, Stephen J. (10 August 2010). "Hub Motors for All-Electric Vehicles Still Have Some Technological Challenges to Overcome". Machine Design.
  20. ^ Whitehead, Andrew; Hilton, Chris. "In-Wheel Motors Roll Again". IEEE Spectrum (July 2018): 27. The Lotus engineers were able to eliminate much of the effect of the added unsprung mass by using slightly more suspension damping. What's more, they found that when that unsprung mass came from actual motors attached to the wheels, the ability to power each side of the car independently improved the car's handling substantially. We've now carried out similar studies on other vehicles. And in all cases, we've found that once the dampers are retuned and we add individual wheel control, the net effect on the vehicle's handling is for the better. So unsprung mass really isn't a showstopper after all.
  21. ^ "Detroit 2011: Mercedes-Benz SLS AMG E-Cell is the color of electric hotness". AutoBlog. 10 January 2011.
  22. ^ Madichetty, Sreedhar; Neroth, Avram John; Mishra, Sukumar; Babu, B. Chitti (September 2022). "Route Towards Road Freight Electrification in India: Examining Battery Electric Truck Powertrain and Energy Consumption". Chinese Journal of Electrical Engineering. 8 (3): 57–75. doi:10.23919/CJEE.2022.000026. S2CID 252841869.
  23. ^ a b Noble, Breana (26 January 2023). "American Axle plows ahead with independence, innovation". The Detroit News. Archived from the original on 26 January 2023.
  24. ^ Crecelius, David (22 June 2021), "Low Cost, High-Performance, HRE-Free 3-In-1 Electric Drive Unit", 2021 DOE Vehicle Technologies Office Annual Merit Review about Electrification, United States Department of Energy
  25. ^ Hag, Johan (2011). Wheel Corner Modules: Technology and Concept Analysis (PDF) (Thesis). KTH Royal Institute of Technology. p. 8.
  26. ^ Eberle, Ulrich; von Helmolt, Rittmar (14 May 2010). "Sustainable transportation based on electric vehicle concepts: a brief overview". Energy & Environmental Science. 3 (6). Royal Society of Chemistry: 689. doi:10.1039/C001674H. Retrieved 8 June 2010.
  27. ^ "Mitsubishi unveils electric car for 2010". NBC News. 11 May 2005.
  28. ^ Spinelli, Michael (1 October 2006). "Let's Motor, Motor, Motor, Motor". Wired.com.
  29. ^ "Honda Worldwide - Tokyo 2005". Honda.com. Archived from the original on 1 May 2006. Retrieved 22 September 2023.
  30. ^ Padeanu, Adrian (17 January 2018). "2006 Citroën C-Métisse: Concept We Forgot". Motor1.com.
  31. ^ Wojdyla, Ben (12 May 2017). "Driven: Protean Ford F-150 All-Electric Pickup Truck". PickupTrucks.com.
  32. ^ Yoney, Domenick (9 October 2008). "Paris 2008: Heuliez, Michelin and Orange wrap a revolution in a plain package". AutoBlog.com.
  33. ^ "Peugeot Shows Two HYbrid4 Concepts, New BB1 EV Concept at Frankfurt". Green Car Congress. 15 September 2009. Retrieved 31 May 2010.
  34. ^ "Hiriko electric city car folds up to save space". Wired UK. 26 January 2012. Retrieved 1 February 2012.
  35. ^ Hitipeuw, Jimmy (30 January 2012). "The Folding Electric Car". Kompas.com. Archived from the original on 2 February 2012. Retrieved 16 July 2012.
  36. ^ Holloway, James (20 February 2012). "Hiriko - the fold-up electric two-seater set for 2013". Gizmag. Retrieved 26 July 2012.
  37. ^ Henrique Ruffo, Gustavo (23 October 2019). "REE Partnership With Hino Shows More On In-Wheel Motor Tech". InsideEVs.
  38. ^ Paul Ridden (12 September 2022), "Aptera Gamma prototype SEV makes public debut in San Diego", NewsAtlas
  39. ^ Bryant, Eric (10 August 2006). "Siemens VDO announces eCorner motor-in-hub concept". AutoBlog.com.
  40. ^ Ulrich, Lawrence (23 September 2007). "They're Electric, but Can They Be Fantastic?". The New York Times.
  41. ^ Wilkinson, Luke (25 June 2019). "Lightyear unveils long-range solar-electric car". Auto Express. UK. Retrieved 26 June 2019.
  42. ^ "Lightyear 0 Production On Hold As Company Focuses On Affordable Model". InsideEVs.
  43. ^ Miller, Caleb (27 June 2023). "Lordstown Files for Bankruptcy, Endurance Pickup Assets up for Sale". Car and Driver.
  44. ^ Cristian Agatie (5 July 2024), "Crazy BMW Coupe Prototype With Neue Klasse DNA and Wheel Hub Motors Emerges From the Void", AutoEvolution
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