In the past decade, most transportation markets, from automobiles to military, aircraft, and even space systems, have shown great interest in hybrid and electric vehicle technologies. In order to obtain the efficiency advantages and green image promised by these vehicles, it is very important to conduct transmission system and component tests during the design and manufacturing process. These tests are specifically aimed at the special nature of hybrid and electric vehicles.

Hybrid and electric drivetrains have several characteristics that make their tests very different from standard tests performed only on internal combustion engine (IC) systems. For example, they use regenerative braking (the energy actually produced by braking is returned and stored in the vehicle's battery for later use). This usually requires the addition of complex AC inverter technology, and usually requires more complex transmissions.

In addition, these vehicles often have several modular control units (MCUs), which are basically small on-board computers that control the functions of major subsystems such as the engine, transmission and charging systems. In order to properly test these components, the test system needs to be able to communicate with one or more of these units through a high-speed vehicle network. This ever-changing technology requires a test system that is completely different and more complex than a test system that is only used for IC systems.

The technology is designed to ensure proper testing and realization of the energy efficiency advantages promised by hybrid and electric vehicles. More importantly, the test technology itself is energy-saving, reduces operating and maintenance costs, and helps improve the overall environmental performance of the vehicle.

Types of hybrid/electric vehicle drivetrain testing Hybrid or electric drivetrain testing is carried out at multiple stages in the vehicle development process, and each stage plays an important role.

Accurate measurement of engineering testing is crucial, so design engineers can extract every point of efficiency from their design. Otherwise, they will lose most of the advantages of using hybrid/electric technology. Most vehicles use three-phase AC motors driven by inverter technology, so a sophisticated power analyzer is required to correctly measure the three-phase AC power with a large amount of harmonic content.

In-process and off-line testing Manufacturing off-line testing is usually used to verify that no defects have been introduced during the manufacturing process and that the components will be executed according to specifications. Typical tests include operational verification, rapid performance testing, and rigorous testing to verify that the high-voltage electrical system is properly isolated, so it can be safely used in vehicles.

You can also perform in-process testing to test some components along the production line. This improves manufacturing efficiency and significantly reduces the chance of defective components entering the finished product.

Quality control testing Quality control (QC) testing is usually performed on a certain percentage of components to verify that they are performed within a specified range and are relatively free of defects. For example, a forklift company may conduct QC tests on a batch of imported electric motors that are planned to be placed in its forklifts. They will use QC testing to verify that the goods from their suppliers comply with regulations and will not have a high failure rate on site. This type of test system is usually less complicated because it does not have to measure as many parameters as those tested in the engineering system, nor does it have to measure accuracy.

Regenerative braking is the basis for improving fuel economy. Hybrid or electric vehicles use four-quadrant motor/inverter technology to assist the engine (hybrid) or as a prime mover (electric vehicle). Four quadrants mean that the motor can control the speed or torque in either direction-the motor can accelerate, run and decelerate, forward or reverse.

During the deceleration process, the system uses regenerative braking, so the electric motor is used to decelerate the vehicle, and in the process becomes a generator, partially recovering the vehicle's kinetic energy and restoring it to the battery. In a hybrid system, when stopping, decelerating, or idling, the engine usually shuts down without burning fuel. At the same time, the electric motor becomes a generator again, partially recovering energy and storing it back in the battery. When it is necessary to keep the vehicle moving or accelerate, the engine will restart. During this period, the electric motor assists in the acceleration of the vehicle, using part of the recovered electric energy to reduce the load on the engine, thereby reducing fuel consumption.

The test procedures used to design and manufacture such vehicles must ensure the effective operation of the powertrain and make full use of this regenerative power.

Hybrid or electric vehicle test system Hybrid and electric vehicle testing is very different from traditional internal combustion engine testing, which usually measures speed, torque, and some temperature, pressure, and flow. Very precise speed and torque control is usually not required when testing internal combustion engines, so dynamometers used for standard internal combustion engine testing (for example, water brake and eddy current) have never been designed to handle the accuracy required for hybrid or electric power systems Level, also can not test the regenerative (electric) operation mode.

Modern hybrid/EV test systems must provide all the functions of traditional systems and increase the ability to test high-power regenerative electric drives, high-voltage batteries and charging systems, and communicate with any number of intelligent control modules (MCUs).

Electrical system testing For many larger hybrid/electric drive systems, the use of higher voltage and higher efficiency drive systems is a strong trend. From the traditional 12/24V DC power system to the 240V AC power system, it usually requires one-eighth or less of the current to provide the same power. Not only is this more efficient, but it also requires smaller/lighter wiring and smaller components to transmit energy, making the vehicle smaller, lighter, and more energy efficient. Many current designs operate at 800V or higher, making the vehicle more efficient.

To perform such tests, a four-quadrant electric dynamometer must be used, which can simulate/test all operating modes in hybrid or electric vehicles. The ability to drive or load in either direction is exactly what the system needs to test itself in this way. When the system is in regenerative mode, the standard dynamometer cannot test the system during braking.

Creating an efficient AC power supply system usually involves the use of inverter-based three-phase technology to precisely control the motors in the system. These systems tend to be very efficient, but they also produce a lot of harmonic distortion in the power output. Therefore, in addition to electric dynamometers, modern hybrid/electric vehicle test systems usually include sophisticated three-phase power analyzers. The device must be specifically designed to accurately measure high-power electrical values ​​with a large amount of harmonic distortion.

In order to meet the system requirements for comprehensive testing of hybrid and electric vehicle drive systems, Sakor developed HybriDyne, a comprehensive test system used to determine the performance, efficiency, and durability of all aspects of the hybrid drivetrain, including electric assist ( Parallel hybrid), diesel electric (series hybrid) and all-electric vehicle systems.

HybriDyne integrates components of Sakor's DynoLAB power system and motor data acquisition and control system. Combined with one or more AccuDyne AC motor dynamometers and one or more precision power analyzers, the modular HybriDyne can use a single system to test individual mechanical and/or electrical components, integrated sub-components, and complete transmission systems.

A key element of high-voltage battery simulation and testing of modern hybrid or electric vehicles is the high-voltage battery and charging system. To accurately test a high-voltage hybrid or electric drive system, you need to be able to provide an accurate and repeatable high-voltage DC power supply. Since battery performance changes over time depending on its state of charge, environmental conditions, and service life, they cannot generally be used to power the DC components of hybrid/EV test systems. To obtain repeatable results, a reliable DC power supply is required. The standard off-the-shelf power supply will not work because it cannot absorb power from the regenerative system. In fact, the standard power supply used with the regeneration system may be damaged or destroyed.

Sakor solved this problem by developing a solid-state battery simulator/test system specifically for high-voltage hybrid vehicle batteries to simulate these batteries in an electric drivetrain environment.

The core of the system is an efficient line regenerative DC power supply. In the regeneration mode, the absorbed power is regenerated back to the AC power source instead of being dissipated as waste heat, which was a common practice in the previous generation of test systems. This innovative approach provides higher energy efficiency and significantly reduces overall operating costs.

The solid-state battery simulator/tester is used in conjunction with DynoLAB to accurately simulate the response of high-voltage batteries under actual conditions. However, since it is not affected by variable charge states, it provides repeatable results, one test after another. When operating as a battery tester, the same unit subjects the battery to the same charge/discharge curve as encountered in actual vehicles on actual roads.

One of the advantages of using an AC dynamometer with a regenerative DC power supply is that when the two are coupled together, the power absorbed by one unit can be recycled back to another unit in the test system. This greatly reduces the power drawn from the AC power source (a reduction of 85% to 90%), thereby significantly reducing overall operating costs. This is a very energy-efficient configuration. During the life cycle of the test system, it can easily recover the cost, usually multiple times. Very low maintenance requirements also greatly help reduce operating costs.

Communication with the control module Communication with a separate control module (MCU) is another function that must be built into a hybrid or electric vehicle test system. In the past, engines were mainly controlled by throttle and ignition. Now, the engine has an engine control unit (ECU), the vehicle may have a separate MCU to control the electric drive, and may have a separate unit to control the transmission and/or charging system. These units usually transfer commands and/or data between them via high-speed vehicle networks (such as CAN, LIN, FlexRay, etc.).

In order to correctly test this complex transmission system configuration, the test system must be able to effectively communicate with these control units at the same time. The DynoLAB system is designed to integrate all these independent units into a single, coordinated test platform.

The automotive, heavy equipment, military, and aerospace industries are very excited about the promise of improving the environmental performance of hybrid and electric vehicles. In order to achieve this promise, it is necessary to adopt a powertrain test program that meets the needs of this emerging technology.

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