Continental is expanding its sensor portfolio for the fast-growing electric car market with the unveiling of a new innovative sensor. The high-speed inductive e-motor Rotor Position Sensor (eRPS) detects the exact position of the rotor in a synchronous electric machine. The machine helps to increase efficiency and enables smoother operations. Compared to existing resolver sensors, the eRPS is more compact and 40 percent lighter in weight. Existing solutions for rotation measurement are often based on the resolver principle (a rotary electrical transformer). That is complicated and needs to be adapted to each type of synchronous motor specifically. The eRPS, however, is a standardized component for every motor regardless of the number of pole pairs. It is easy to carry over this sensor from one motor to another. The start of production is planned for the end of 2025.
“The growth in vehicle electrification translates into more synchronous motors in the car. This ranges from big and powerful ones like traction motors to smaller ones like electric pumps. Our standardized eRPS technology has a wide range of potential applications in electric vehicles,” said Laurent Fabre, head of the Passive Safety and Sensorics Segment at Continental. “Measurement precision, compact dimensions, and the all-in-one sensor concept combining several functions add to a high level of integration in the car.”
Compactness and precision make the eRPS the ideal choice for electric mobility
The eRPS was specially developed to control synchronous motors. To achieve maximum motor efficiency, the motor control unit needs to know the exact position of the rotor. This type of sensor is an essential part of synchronous motor applications. The resolver is a comparatively massive sensor. The eRPS is very flat and supports compact motor designs with a small overall length. The sensor design is based on eddy current principle. It is optimized to increase robustness to mechanical tolerances. State-of-the-art integrated circuits (ICs) are used for signal processing. The IC has been designed according to ISO 26262 functional safety automotive standards to reach ASIL C. As an option, two ICs can be embedded in the eRPS to ensure the redundancy that is an integral part of functional safety.
Though the traction motor of an electric or hybrid vehicle is a prominent use case, there are many more synchronous motors in electrified vehicles. Future dry-brake systems (without hydraulics), for instance, will also be actuated electrically. When developing the eRPS, Continental took on existing knowledge and experience with inductive technology. For example, the brake-by-wire system MK C2 uses an Inductive Motor Position Sensor and has been a benchmark for the sensing concept development with increased speed and accuracy, as is the case with the eRPS.
Precision motion detection via inductive technology
The new eRPS is an inductive rotor position sensor covering several integration configurations. The sensor can be mounted through the shaft, or it could be integrated at the end of the rotor shaft, including in this case the sealing function. The module contains excitation and reception coils embedding one or two ICs that detects directly the electrical angular position of the metallic encoder on the rotor shaft. This straightforward and weight-efficient solution delivers an output in a format that requires minimal signal post-processing. The electrical angular position data is required for efficient e-machine torque control and to achieve the maximum service life of a motor.
“The signal pattern of the eRPS is much easier to work with than that of a resolver. The measurement principle is very fast, extremely robust, and is suited for high motor speeds and acceleration. It is very compact and works with a minimal number of parts,” said Ronan LeRoy, head of the Sensors and Subsystems Product Center in the Passive Safety and Sensorics Segment at Continental.
Comprehensive portfolio of sensors for the engine and battery of electric vehicles
The eRPS is extending Continental’s sensor portfolio specifically designed for electromobility to support both, road safety and electrification. With the Current Sensor Module and Battery Impact Detection, the company already introduced in the year 2022 two new solutions focusing on protecting the battery and/or on battery retention of electric vehicles.
Continental develops pioneering technologies and services for sustainable and connected mobility of people and their goods. Founded in 1871, the technology company offers safe, efficient, intelligent, and affordable solutions for vehicles, machines, traffic, and transportation. In 2021, Continental generated sales of €33.8 billion and currently employs more than 190,000 people in 58 countries and markets. On October 8, 2021, the company celebrated its 150th anniversary.
