Resolver: The Key Sensor in Electric Vehicle’s Electric Drive System

As technology advances, various fields such as automobiles, rail transportation, and mechanical industries are gradually moving towards "electrification". The electric drive system is the core of achieving electrification, providing power and control for electric equipment. The drive motor is the power generation device of the electric drive system and typically operates in complex environments of high temperature, high humidity, and strong vibrations. While drive motor works, its position and speed information need to be reliably, frequently, and accurately transmitted to the electric control system to achieve precise control of the drive motor.

Among sensors that provide angular position sensing functionality, resolvers hold an irreplaceable position due to their high reliability, precision, duration, and suitability for various complex environments, especially in military, aerospace, aviation, and maritime applications. However, due to the complexity of signal processing circuits, early manufacturing and usage of resolvers were costly, limiting resolvers application scope. In recent years, with advancements in signal processing technology, signal processing for resolvers has become simpler and more efficient, significantly expanding their application range. They are now widely used in applications with strong vibrations, large temperature variations, high humidity, and oil contamination, such as electric vehicle’s electric drive systems, textile machines, injection molding machines, mining machines, CNC machines, and wind power machines.

Currently, the primary application areas for resolvers include industrial servos, aerospace, electric vehicles, and rail transportation. According to MarketWatch, the global resolver market is expected to grow from $3.72 billion in 2021 to $10.44 billion in 2028, with a compound annual growth rate of 15.90%; also, it is estimated that the global resolver market in 2022 is $4.31 billion, with China being the largest market, accounting for approximately 40% of the global resolver market share and indicating significant growth potential. According to reports from The Express Wire, the primary application of resolvers globally is the industrial sector, accounting for approximately 35% of the market share, with major players including Danaher (USA), Tamagawa Seiki (Japan), LTN (Germany), TE Connectivity (Switzerland), Honeywell (USA), Woodward (Germany), and AMETEK (USA). The aerospace and defense sector follows closely, accounting for approximately 30% of the resolver market, with key participants including Danaher (USA), Tamagawa (Japan), Moog (USA), LTN (Germany), TE Connectivity (Switzerland), and Honeywell (USA). In the emerging field of electric vehicles, resolvers currently represent around 3.5% of the market share, but due to EV’s low global penetration rate and their rapid growth, this EV’s resolver market has significant growth potential. Major participants in this sector include Tamagawa Seiki (Japan), Yingshuang (China), Minebea Mitsumi (Japan), TE Connectivity (Switzerland), and Changzhou Huaxuan (China).

This article will focus on the application, competitive landscape, and future development of resolvers in the electric vehicle sector.

1. The Application of Resolvers in Electric Vehicles

A resolver consists of a rotor and a stator. The rotor is driven by the EV’s drive motor. The electromagnetic coupling between the stator and the rotor results in an induced voltage. This induced voltage has a strict functional relationship with the rotor's angle of rotation. By measuring and calculating the dynamic induced voltage, precise measurements of the rotational angle displacement and angular velocity of the rotating machinery can be obtained. This data can be decoded into the rotor's instantaneous position and speed, thereby enabling accurate measurement and sensing functions for electric drive systems in various fields, including electric vehicles, industrial servos, rail transportation, aerospace, and etc..

Typically, in PEVs, one vehicle is equipped with one driving motor and thus one resolver. In PHEVs, one vehicle may be equipped with two or more driving motors. Multiple driving motors enhance driving power, and high-quality resolvers enhance driving safety and comfort, maximizing the mechanical performance of the motors. In recent years, electric vehicle manufacturers have gradually introduced vehicles equipped with multiple driving motors. For example, Tesla introduced the Model S Plaid in 2021, which featured 3 driving motors, while BYD introduced in 2023 the "Yangwang" series that was equipped with 4 driving motors. Exceptional electric drive motor systems significantly improve the mechanical and driving performance of electric vehicles.

2. The Competitive Landscape of Resolvers in Electric Vehicles

With the rapid growth of the electric vehicle industry, the field of resolver is facing new opportunities of development. According to "The White Paper of the Development of China's Electric Vehicle Industry (2023)" published by EVTank and China YiWei Institute of Economics, global sales of electric vehicles have increased from 208 thousand units in 2013 to 10.82 million units in 2022, with a CAGR of 48.47%, and the market penetration of electric vehicles has risen from 0.08% to 25.64%. It is projected that global sales of electric vehicles will reach 25.42 million units in 2025 and 52.12 million units in 2030. This suggests that the market penetration rate of electric vehicles will continue to rise and is expected to surpass 50% by 2030.

According to the data from Clean Technica, the estimated global sales volume of EV resolvers in 2022 is expected to be 14.1 million units. The sales volume, revenue, and market share by the leaders are calculated as follows:

As indicated in the table above, the global EV resolver market is primarily dominated by companies such as Tamagawa Seiki and Yingshuang. These market players primarily supply EV resolvers to leading EV manufacturers such as Tesla and BYD.

Since 2009, China has been, consistently, the world's largest automobile market and one of the most significant markets in the automotive industry. According to Jibang Consulting, in the field of electric vehicles, China has been the global leader in sales for 8 consecutive years. In 2022, China's sales of electric vehicles accounted for over 50% of the total global sales, demonstrating its position as the EV vehicle market in the world.

The Chinese electric vehicle market reached a turning point of growth in 2021, and the growth rate continues to rise. In 2021, Chinese electric vehicle sales increased by 157.48% compared to 2020, and in 2022, the sales increased by 95.61% compared to 2021. The market penetration rate of electric vehicles in Chinese automotive market has increased rapidly as well, rising from 2.69% in 2017 to 25.64% in 2022. According to the forecasts by Frost & Sullivan, by 2026, the market penetration rate of electric vehicles in the passenger car market in China will increase to 50.30%.

According to statistics and market data compiled by the China Passenger Car Association, the estimated sales volume of resolvers in the field of electric vehicles in China for 2022 is expected to be 8.6 million units. The sales volume, revenue, and market share by the leaders are calculated as follows:

As shown in the table above, the Chinese market for EV resolvers is primarily dominated by companies such as Yingshuang and Tamagawa Seiki. These market players mainly supply resolvers to leading Chinese electric vehicle manufacturers such as BYD, SAIC-GM-Wuling, Tesla China, Guangzhou Automobile Group, Geely, and etc..

3. The Future Development of EV Resolvers

The field of electric vehicles represents an emerging application for resolvers, and the resolvers’ future development is closely tied to the development of the electric vehicle industry.

1. The penetration rate of the electric vehicle is continuously increasing.

According to research reports, in 2022, the global penetration rate of electric vehicles was approximately 13.43%, while China's EV penetration rate was about 25.64%; both rates were still relatively low. According to the China Association of Automobile Manufacturers, in August 2023, the sales of EV accounted for 32.80% of China’s total automotive sales, and from January to August 2023, the sales of EV accumulatively accounted for 29.50% of China’s total automotive sales. Furthermore, Qing Wang, Deputy Director and Research Fellow at the Institute of Market Economy of the Development Research Center of the State Council, predicts that by 2025, China's sales of electric vehicles will reach around 17 million units, and by 2030, the market share of new automobile sales will surpass 90% with approximately 32 million units.

2. The number of electric drive motors in electric vehicles is increasing.

With the development of the electric vehicle industry, the supply chain is gradually maturing, and the manufacturing costs for automakers are continuously decreasing. "Dual-motor all-wheel-drive" configurations are also becoming more popular, transitioning from high-end models to more economical ones. EVs such as Tesla Model Y, BYD Tang, BYD Song are equipped with dual motors, and Great Wall Motors has introduced the dual-motor "four-wheel-drive hybrid technology aka 'Hi4’” that is expected to be widely adopted. The number of electric drive motors in EVs corresponds to the number of resolvers needed. As the number of electric motors in electric vehicles increases, the demand for resolvers will also see a significant increase.

3. The rapid development of resolvers places higher demands on design and manufacturing techniques.

Efficient and energy-saving motors are crucial for the development of electric motors and are one of the key technology breakthroughs supported by Chinese policies. Light-weighted design is one of the important areas for achieving high-efficiency and energy-saving motors. The Resolver, as a type of MEMS motor, serves as high-precision position sensor for driving motors. Resolvers contribute to improving the efficiency of the EV drive system, thereby reducing the overall energy consumption of the motor.

With the emergence of new types of electric drive systems such as "multi-in-one motors" and "oil-cooled motors", light-weight and integration have become the trends for future developments. Resolvers are also being optimized through structural redesign and processing improvements to meet the evolving requirements of future electric drive systems. For example, in the case of "oil-cooled motors", the working environment for the resolver changes to one immersed in automatic transmission fluid (ATF), placing higher demands on the resolver’s oil resistance and insulation performance.

In summary, the rapid development of the electric vehicle industry presents a significant opportunity for the growth of the EV resolver industry. The technological advancements driven by this rapid development facilitate the continuous expansion of the applications and competitive advantages of the resolver in the fields of industrial servos, aerospace, and etc..