On June 17-18, 2021, hosted by NE Times, Shanghai Electric Drive Co., Ltd. and Huayu Automotive Electric System Co., Ltd. strategically cooperated, and the "2021 Global xEV Electric Drive System Technology and Industry Conference" jointly named by Jingda Co., Ltd. It was successfully held in Jiading, Shanghai.

The following is the transcript of Huang Yan's speech from Changzhou Huaxuan, with the theme of "Resolver Solutions under High Pressure Oil Cooling Drive System".

 

 

Today, I will share with you the system solution about resolver. It is mainly divided into four aspects: the structure selection and system layout of the first resolver. The second reliability test in the oil-cooled environment, Huaxuan's resolver was first mass-produced in 2019 among oil-cooled motors. It has been running for more than two years now, and its performance is very stable, so it has accumulated some in the experiment. experience. The third is the EMC solution of resolver in high-voltage systems. When resolver is distorted during waveform acquisition, how to solve it at this time. The fourth resolver's solution for end-of-line testing. Most of our customers' resolvers are not tested for performance when they are put into storage, nor are they tested when they are offline.

Resolver is a precise speed and position sensor. With the trend of more and more integrated design of the drive system, it is more used in high-voltage drive platforms, oil-cooled motors, three-in-one or even all-in-one structures. In the use environment of direct drive single motor for several years, the resolver allows the layout space to be more compact and the application environment is more severe. What new problems do we need to pay attention to? The most common occurrences are unreasonable structural layout in the design process, electromagnetic interference in the analysis process, assembly deviation in the assembly process, and material life evaluation in oil-resistant environments. Let's discuss it together today.

First of all, when arranging the structure, you need to pay attention to the following points:

(1) The cooperation between the motor and the shaft:

In the selection of shaft material and the control of residual magnetism, we have encountered the situation where the residual magnetism is too high at the position where the resolver rotor is assembled, and distortion occurs at high speed, so in the early development process, it is necessary to evaluate, different resolver Ability to resist interference to residual magnetism and matching of shafts.

Under different motor speeds, the selection of the interference between the rotor and the shaft. We have done a simulation for the customer and found that when choosing one of our standard resolvers, there is a risk of clearance and separation between the rotor and the shaft at high speeds. Therefore, we suggest that you must do some simulation in the early selection process, because the topology design of the resolver rotor is completed by us, and the design of the riveting point is also designed by us, but the amount of interference is required by the customer. It is necessary for us to complete the risk assessment and structural design together with the customer.

The press-in process and the tooling pressure plate are matched to the pull-out force of the rotor rivet point. There are many ways to press in the resolver rotor and shaft, including the common clearance fit, interference fit, matching shrink fit or cold pressing. But how to press in to minimize the deformation of the rotor and the damage to the shaft? This involves the selection of press-in tooling, the selection of press-in force, the selection of the number of resolver riveting points, etc. The ultimate goal is to make the resolver rotor No flakes, minimal deformation. This is also a problem that our resolver manufacturers and customers need to discuss together. We also recommend that customers do a shaft imitation test in the early development stage, and different matching sizes and different resolver interferences are matched to obtain the optimal parameters under the matching conditions of different pressing force coefficients.

Next, let’s talk about the choice of rotor and keyway. Some customers need smooth holes, and some customers need keyways. What is the right one? Our suggestion is that if you need keyways, try to make them as symmetrical as possible, so that the rotor mold can be With the rotary scheme, the resolver accuracy will be better and more stable. However, attention should be paid to the tolerance and processing consistency of the matching keyway, otherwise, in the case of high speed, assembly deviation will occur, resulting in zero drift.

 

 

(2) Matching of motor end cover:

Avoid the installation method of the interference fit between the resolver stator and the casing, and avoid the magnetic conduction of the installation structure and the pressure plate. The selection of the off-line zero adjustment scheme is matched with the stator structure. The stator structure design and rotor structure design will be related to the zero adjustment method used in the process. Common zero adjustment methods include manual zero adjustment, offline test method, and online self-learning method, which will not be described here. From our point of view, it is suggested that the relative positions of the stator and rotor mechanical positioning should be as uniform as possible in the design, so as to reduce the deviation, thereby improving the efficiency and accuracy of zero adjustment. Because the initial measurement angle deviation will also have an impact on the efficiency consistency behind the motor.

(3) Power system coordination:

The following points should be paid attention to here: the influence of the limit size error of the resolver on the electrical performance under the calculation of the assembly installation dimension chain, the wiring harness structure layout, the EMC generated by the layout of the high and low voltage wiring harnesses, the shielding treatment of the resolver wiring harness, the resolver signal at different temperatures Variations and matching and compensation of controller systems, etc.

The deviations that we will produce in the assembly design process include axial deviation, radial deviation, inclination and so on. These deviations will cause changes in the electrical properties of the resolver. Therefore, in the early development process, we should pay attention to the adaptability of the electrical properties of the resolver in the case of extreme assembly. This can be done in the form of simulation or actual measurement. You can see the data we simulated on the picture, the axial deviation will make the resolver ratio smaller, and the radial deviation will make the resolver ratio larger. At the same time, the radial deviation has a great influence on the resolution of the resolver, so we need to consider the matching of the resolver performance and the controller under the limit size from the structure, and we need to select the appropriate air gap and accuracy. At the same time, the electrical properties of the resolver will also change at different temperatures. We generally give a suggested function change, and the controller can be used for the corresponding temperature compensation.

 

 

 

 

Let's share the reliability test of the resolver in the oil-cooled motor.

It mainly depends on the durable conditions required by the working conditions of the whole vehicle, such as temperature cycle, high temperature storage, oil cooling high temperature cycle and so on. But in general, the oil cooling experiment is not a simple oil, and a certain proportion of water needs to be added. Because the motor usually produces a small amount of condensed water, the proportion of water needs to be kept the same in each experimental stage. We usually test the electrical performance of the resolver in the middle of the experiment, and compare and analyze the electrical performance before the experiment to see how much the change is. In addition, enameled wire dismantling, glue physical property test, plastic parts aging mechanical experiment and so on will be carried out. It is especially important to note that different oil products will produce sediment, and the sediment and oil spray surface will affect the resolver performance and durability, so different protective structures need to be considered. After all, the product needs to be used for 10 or even 15 years, we need to know what is the limit life of the material?

Our company's experiments on vibration shock and mechanical frequency sweep of oil-cooled motors are carried out by simulating the actual working conditions as much as possible, making a sealed cavity, installing the vent valve matched by the customer, and even carrying out some working conditions with rotating speed. By simulating the actual working conditions as much as possible, the impact of various harsh working conditions on the product is evaluated. Here we need to pay attention to the wiring harness layout. Under different welding methods and different assembly layouts, how many risks are caused by the bending radius of the wiring harness. It is recommended to perform simulation in advance, so as to choose different ways of fastening the wire.

Let's share the EMC solution of resolver in high pressure system.

EMC should be said to be a big subject close to metaphysics, and today only the structural arrangement will be shared. In the early development process, I suggest to simulate the resolver model and system assembly, and first confirm whether the system interference source will affect the accuracy of the resolver body. If there is an impact, judge whether the interference belongs to the axial interference or the radial interference, so as to choose the appropriate structure to avoid it. In the early days of new energy, everyone was used to using Japanese brands, and there were not many models that were structurally compatible with independent development platforms. This requires us to do a full assessment in the early stage. If the platform dimension is enough to support, it is more recommended to carry out a separate resolver development. The resolver structure used by Tesla in the picture is very special. When we analyze his initial matching, he considers the radial magnetic isolation problem.

The other is the experiment. Most of the EMC experiments are carried out at the PV stage. At this time, if problems are found and the structure is changed, it will involve end caps, resolver rotors, resolver pressure plates, resolver bodies, and wire harness shielding grounding. Wait, there is very little room for change. Therefore, we suggest that the resolver waveforms and excitation power supply lines at different speed sections must be collected in advance in the early development process to ensure that the sine and cosine waveforms at the full speed section will not be distorted. At present, our company can realize the acquisition of resolver waveforms at a speed of 30,000 revolutions, ensuring that the resolution of the resolver is good at full speed. Finally, let’s talk about the wire harness hinges. In different assembly system designs, different handover densities and grounding methods bring different anti-interference capabilities.

 

 

Finally, share the resolver offline test.

Now the accuracy and electrical performance of the resolver are basically guaranteed by the resolver manufacturer. We did an experiment with a Japanese customer. The same batch of resolvers was marked after the performance test was done at the factory, and the motor assembly was assembled one by one. After they are offline, the accuracy test is carried out, and the degree of dispersion is different. This also fully illustrates the different effects of the resolver assembly and system structure matching that I just mentioned on the resolver performance. Therefore, we recommend that domestic manufacturers learn the control methods of Japanese manufacturers, and conduct the offline accuracy test after the resolver assembly is assembled to avoid performance failure under extreme assembly conditions. On the other hand, it can effectively control the consistency of assembly.

 

 

In addition, there are also wiring errors that often make mistakes. We have sorted out the six lines and there will be 16 error reporting methods. Many customers' connectors are made by themselves, and errors may occur at this time. It can be matched with a resolver wiring inspection instrument to avoid the situation of motor reversal after installation. At present, Huaxuan can also help customers to assemble and deliver the connectors together. Our company can perform this wiring test when offline. When the hybrid system is tested offline, some customers will choose the speed fluctuation test, the resolver waveform decoding test method and so on.

Changzhou Huaxuan Sensing is currently supporting many OEMs such as SAIC, GM, BYD, Dongfeng, Lili Automobile, etc. It is also a qualified supplier of ZF, United Electronics, Inovance Technology, Nidec and other enterprises. The company has branches in Europe, which can directly provide face-to-face technical services to European customers. The main purpose is to provide customers with a systematic solution of resolver, including system structure matching design, process route plan, off-line test plan, etc. I hope that on the road of new energy vehicle development, we can make a contribution to the localization of key core components. Huaxuan will be the best resolver in China!