The position lock sensor detects whether the electric vehicle (EV) charging connector is properly locked into place during the charging process. This safety feature prevents accidental disconnection or removal of the charging cable while charging is in progress.
This article presents three sensor types that can detect the presence of the EV charging cable. The first sensor is the direct and commonly used one for EV charging cable locking. However, we also see interesting use cases of two other sensor types suitable for the same purpose.
The most commonly used position sensor type
Figure 1 shows the HAC 3930, a 3D Hall-effect position sensor designed specifically for EV charging. The sensor can accurately detect the position of the locking pin or actuator in the charging connector. It can measure angular positions up to 360° or linear movements, making it suitable for various locking mechanism designs.
Figure 1. An illustration of the HAC 3930 sensor’s placement behind the EV charging connector and block diagram of the HAC 3930. (Image: TDK-Micronas GmbH)
The sensor’s stray-field compensation feature is critical in an EV charging environment where strong electromagnetic fields may be present. This feature ensures reliable position detection, even in the presence of external magnetic interference, providing a secure and reliable solution for EV charging systems.
The sensor is designed as a Safety Element out of Context (SEooC) ASIL B ready according to ISO 26262, which is essential for automotive safety-critical applications like charging connector locks.
The HAC 3930 supports various measurement setups, including angular measurements with stray-field compensation and linear position detection. This flexibility allows it to adapt to different charging connector lock designs. The HAC 3930 also provides either PWM or SENT digital output, which can be easily integrated with the vehicle’s control systems to monitor the lock status.
Figure 2. A BML SF2 magnetic encoder for safety system.(Image: Balluff Inc.)
It can operate in ambient temperatures from -40° to +150° C and is suitable for various environmental conditions an EV might encounter. With a typical supply current of 8 mA, it’s suitable for energy-efficient operation in EVs.
Magnetic sensors
Do magnetic sensors find a place in an EV charging cable for locking purposes?
Yes, they have! The BML SF2 magnetic encoder, shown in Figure 2, is not specifically designed for locking electric vehicle chargers. However, its features and capabilities could be adapted for EV charging applications.
To adapt the BML SF2 for EV charger locking, the magnetic tape could be installed along the path of the locking mechanism. The sensor head could be mounted on the moving part of the lock. The precise position feedback could be used to confirm when the lock is fully engaged or disengaged.
The BML SF2 offers very high repeat accuracy (<1 μm) and system accuracy of ±12 μm at a mounted distance of up to 1 mm. This level of precision could be valuable in detecting the exact position of a charging connector or locking pin in an EV charging system.
The encoder is certified for applications up to Safety Integrity Level 2 (SIL 2) and Performance Level d (PL d). This makes it suitable for safety-critical applications like properly locking a charging connector.
With an IP67 rating and the ability to operate from -20°C to 80°C, it could withstand various outdoor conditions typical of EV charging stations. Its small dimensions (12 x 13.1 x 35 mm) could allow for easy integration into the limited space of a charging connector housing.
Stereo camera systems
Is a stereo camera system worth trying to use as a position sensor?
Figure 3. A ZED 2i depth sensor. (Image: DeviEstore)
Researchers have done that! The ZED 2i depth sensor (Figure 3) is a sophisticated stereo camera system developed by Stereolabs, designed to capture high-quality depth maps and 3D spatial data.
The sensor has been found to be applicable to EV charging cable locking, as demonstrated by researchers from the University of Dunaujvaros and the University of Obuda from Hungary. The ZED 2i depth sensor detects and extracts the position of the Combined Charging System 2 (CCS2) socket on the electric vehicle. It captures RGB images and depth information of the vehicle and charging socket area.
The system uses image processing techniques to determine the charging socket’s exact position and tilt angles. This information guides a robotic arm in positioning the charging plug precisely. Figure 4 shows a glimpse of the process of finding the position of the CCS2 connector.
By providing accurate spatial information, the ZED 2i enables the robotic system to connect the charging plug correctly and securely to the vehicle’s socket.
The research shows the sensor is a viable solution for automatic charging, where a robotic arm can automatically fit the charging cable into the charging socket connector without manual intervention. However, commercializing this approach is still a long way to go.
Figure 4. A step-by-step process where the socket is detected and captures the RGB image for depth of information of the CCS2 connector. (Image: MDPI)
Summary
Most position sensor types can detect the presence of a charging cable during EV charging and proceed to lock. These sensors need high accuracy and resolution to spot the presence and movement of the charging cable. For this purpose, a 3D Hall effect position sensor can be the ideal option. However, other types of sensors, including those discussed in this article, are also worth considering.
References
- Electric vehicle charging connector lock application | TDK-Micronas, TDK-Micronas, YouTube
- HAC 3930 Documentation, TDK-Micronas GmbH
- BML SF2 magnetic encoder system for safety, Balluff Inc.
- Study on Automatic Electric Vehicle Charging Socket Detection Using ZED 2i Depth Sensor, Electronics, MDPI
Images
- Figure 1, TDK-Micronas GmbH
- Figure 2, Balluff Inc.
- Figure 3, DeviEstore
- Figure 4, Electronics, MDPI, Page 20, Figure 16
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Filed Under: FAQs, Sensors