Overview of Automotive Electronics Measurement System Solutions

With the increase of electronic systems in automobiles, how to efficiently test highly mechatronic automobile systems has become a challenge faced by Chinese test engineers. As this article addresses various testing issues involved in the automobile R&D process, Yokogawa Electric introduces a complete solution that meets the needs of engine, drive, vibration, environmental impact, fuel cell efficiency and CAN bus testing.

With the development of the automobile industry and the electronics industry, more and more electronic technologies are being applied to modern automobiles. Automobiles will also develop from simple mechanical products to advanced mechatronics products. As real-time driving information systems and multimedia devices are popularized in automobiles, automobiles are more personalized, versatile, safe and comfortable. Wireless and mobile computer technologies are developing rapidly, and even if you drive alone in a strange land, you will not feel lonely or lost. Cars are not just a means of transportation in people's lives, but gradually become a way to enjoy life. Research in the field of automotive electronics has become the most active part of automobile research and development, and the achievements made in this area will gain greater returns in the market.

This article introduces the various test solutions provided by Yokogawa Electric for engine analysis, drive analysis, vibration analysis, environmental impact, fuel cell efficiency analysis, CAN bus analysis, etc. involved in the automobile development process (Figure 1).

Testing of fuel cells for electric vehicles

For engineers engaged in automotive R&D, the following aspects are important factors affecting test efficiency and results:

1. Various high-frequency and low-frequency, high-power and low-power electromagnetic radiation interference

2. Common mode voltage, vibration, and changing environment

3. Reliability of data collection and analysis

4. Power supply and energy consumption of the equipment during road test

5. Easy to move and use on site

By communicating with test engineers from automobile production and R&D companies, Yokogawa Electric has continuously improved its products to make them more suitable for the needs of automobile research and development. For example, in order to meet the research needs of electric vehicle fuel cells, Yokogawa Electric developed the DAQMaster series MX100 based on the DARWIN series.

Because each battery only outputs 0.8-1.5VDC, in order to output sufficient power. Fuel cell stacks are generally composed of about one hundred single cells, especially for automotive applications, the battery stack will be composed of six hundred single cells. The cell voltage monitoring (CVM) system can detect problematic cells by testing the voltage of each single cell in the battery stack structure; analyze the battery performance on site or when running for a long time with load.

Differential inputs are used when sensing battery voltage. Although the voltage of a single cell is not high, the differential input terminals can generate several hundred volts to the ground of the test instrument. This voltage is called common-mode voltage. Most data acquisition instruments (DAQ) do not have isolation and the input voltage limit is generally 5 or 10 volts. In addition, non-isolated instruments are often susceptible to ground loops. To overcome the high common-mode voltage problem in fuel cell CVM systems, high voltage isolation is required. Although external signal converters or buffers can be used, many DAQ systems now have built-in buffers to reduce size and cost while maintaining high signal resolution and accuracy.

MX100 DAQMaster provides the highest level of channel-to-ground, module-to-module and channel-to-channel isolation. In addition, its modular structure and standard software make it easy to monitor battery voltages of up to 1200 channels.

The design of a DAQ system that achieves high voltage isolation and multi-channels is a challenge because most data acquisition instrument modules use a single AD converter combined with a front-end multiplier or scanner. The high common-mode voltage signal must pass through a switching relay before being isolated and discretized by the isolation transformer and AD converter.

The MX100 uses Yokogawa's patented high-voltage solid-state semiconductor relay in the scanner to achieve switching of multi-channel input signals. This relay is composed of a high-voltage (1500VDC), low-leakage current (3nA) MOSFET (metal oxide semiconductor field effect transistor) and a voltage output photocoupler. It has the advantages of 10-channel high-speed scanning within a 1-second cycle, no contacts, long life, and no noise.

In addition, the isolation transformer and integral AD converter inside the MX100 are also patented technologies of Yokogawa. Other DAQ systems that use electromagnetic relays to provide insulation will cause problems with switching time, switching stability, and daily maintenance. Finally, the MX100 DAQMaster provides high-performance insulation and simultaneous sampling of 4 channels because the hardware of each channel of the 4-channel module is composed of independent hardware.

For the correct reproduction of waveforms, the sampling rate is very important, and high-speed acquisition can obtain correct data. For this reason, the minimum measurement cycle of MX100 is 10ms, and 3 measurement cycles can be mixed in one system, and the measurement cycle can be set for each module separately. MX100 supports CF cards with a maximum capacity of 2G Bytes. When communication fails, data backup starts. When communication returns to normal, it automatically starts to transmit data to the PC again. MX100's high-speed/multi-channel/high-voltage/multi-cycle characteristics for fuel cell testing help test engineers improve test efficiency and accuracy.

CAN bus analysis

The automotive bus technology is widely used in today's automobiles. The automotive bus provides a unified data exchange channel for various complex electronic devices, controllers, measuring instruments, etc. inside the car. The number of components controlled by the electronic control unit (ECU) in the car is increasing, such as electronic fuel injection devices, idle speed control (ISC), anti-lock brake devices (ABS), airbag devices, electric door and window devices, active suspension, etc. With the widespread application of integrated circuits and single-chip microcomputers in automobiles, the number of ECUs in the car is increasing. As a result, a new concept - the concept of the on-board controller area network CAN came into being. CAN was originally developed by the German BOSCH company as a data communication protocol to solve the data exchange between control and test instruments in modern automobiles. According to the relevant ISO standards, the topology of CAN is a bus type, so it is also called CAN bus.

With the widespread use of CAN bus, the testing and analysis of bus signals in various aspects of automobile research and development, production, and maintenance are becoming more and more important, especially the observation and analysis of noise signals.

Abnormal phenomena caused by reflection noise caused by cable wiring length, terminal impedance position, or overload level changes when connecting multiple contacts can be captured and displayed using the CAN signal trigger of the DL7400 series. The analysis based on the CAN protocol is displayed together with the waveform signal in the form of a list. The trigger condition can be set to a field or multiple fields of the CAN data frame (ID, Data, RTR bits, etc.). The trigger can also be activated at the error frame. The captured CAN bus waveform data can be analyzed on the time axis, and the ID and data of each frame are displayed in hexadecimal or binary symbols.

Battery voltage fluctuation when ABS is working

The ABS control unit monitors whether the wheels are locked by comparing the signals from the speed sensors attached to each wheel. When the ABS control unit detects that a wheel is locked, it sends a signal to the ABS actuator to open the valve. The ABS actuator consists of a solenoid valve, a pump, a motor, and a brake fluid tank. Opening the valve can instantly reduce the disc hydraulic pressure, weaken the braking force, and restore the wheel speed. Then the disc hydraulic pressure is quickly increased again, and the braking force is increased through the ABS actuator. In other words, the brakes can be prevented from locking by increasing or decreasing the disc hydraulic pressure. Increasing the disc hydraulic pressure, that is, using the pump to press the fluid into the cylinder, causes the pump motor to work quickly. This fast motor will affect the PWM current signal that controls the solenoid valve. Normal ABS operation cannot determine whether this affects the battery voltage fluctuation. Therefore, it is necessary to observe this battery voltage fluctuation.

The DL750 Max.1GW long memory allows high-speed sampling to capture all braking actions from start to finish. After capturing the entire process, the zoom function can be used to test a certain irregular part in detail. This function can automatically set the automatic test area of ​​the waveform parameters, including the zoom area. This zoom function can not only accurately test the irregular parts of a cycle, but also automatically test the waveform parameters in the zoom area.

Power steering control ECU (including inverter)/motor development

Power steering (EPS) is already widely used in small cars, but a 3-phase motor is required for large cars that require large torque. Unlike traditional DC motors, testing a 3-phase AC motor requires a power meter to test power and efficiency. In addition, CAN bus communication is used between ECUs, and the CAN bus signal must also be tested.

DL7400 can trigger specific ID/Data on the CAN bus to achieve synchronous observation with other signals. The general oscilloscope DL1640/DL1740 can test the CPU signal of the ECU. Using a 100MHz differential probe and a 150A current probe, it can also test the surge current of the motor. The DL750 has a maximum of 16 channels of isolated input, which is suitable for long-term observation of the input and output voltage/current of the inverter and the ECU control signal. The WT1600 can evaluate the primary DC and secondary 3-phase current/voltage/power of the inverter for the 3-phase drive system of the EPS of large automobiles, and the inverter efficiency. The cumulative power test can also be performed for specific operating modes. The time module/CAN module/isolated A/D module/temperature module of the WE7000 can achieve multi-channel comprehensive testing. Multi-channel long-term simultaneous testing of steering angle/consumption current/voltage/temperature, etc. The CAN module can convert the data on the CAN bus into physical quantities to achieve simultaneous testing.

Direct injection diesel engine injection test

Direct injection diesel engines can reduce fuel costs and purify exhaust emissions. The following is a solution to the key to its development - high-pressure injection and electronic control performance evaluation method:

1. Evaluation of mechanical design values ​​(injection time and injection pressure)

The test objects are the injection pressure of the fuel ejected from the nozzle, the engine speed change and the opening and closing time of the nozzle solenoid valve. Engine development requires dynamic testing (gradually increasing the engine speed to check whether it meets the design requirements) and static testing (checking whether the operation is stable under a fixed speed state).

2. Synchronous test with ECU control signal

Synchronize the test with the ECU control signal to test the ECU timing and actual injection timing.

Conclusion

Due to its extensive cooperation with vehicle and parts companies around the world, Yokogawa has many test cases in this field. Yokogawa hopes to contribute to the development of automotive electronics, solve more test problems in cooperation, and create more application cases of Yokogawa products. For more information about Yokogawa, please visit www.ysh.com.cn.

Author: Han Ying

Sales Engineer

Shanghai Yokogawa International Trading Co., Ltd.

Email hanying@ysh.com.cn