Maintenance Motion Hybrid Simulation And Human Factors Automatic Evaluation For Entire Maintenance Processes In Virtual Environment

Maintainability is an important characteristic of complex equipment, poor maintainability design not only increases the maintenance cost, but also reduces the utilization. Complex equipment with electro-hydraulic systems has the characteristics of diversity, complexity, randomness, and environmental sensitivity, which cause a large number of maintenance technical orders(MTOs) need to be simulated and evaluated in product development and design phase. With the trend of more complexity and technology in equipment, current simulation and analysis tools are difficult to meet the requirements of maintainability concurrent design owing to low efficiency of MTO simulation and evaluation.To solve the problems above and satisfy the concurrent design requirements of complex equipment, methods and technologies for maintenance hybrid simulation and human factors automatic evaluation for entire maintenance processes in VE are researched. The main research works of this thesis are summarized as follows:1. A maintenance motion hybrid simulation method is presented based on a detailed analysis of VH control methods in maintenance simulation. The basic idea of the proposed method is make full use of the advantages of different maintenance simulation modes. After detailed analysis of maintenance work’s basic processes, maintenance motion is divided into three types: primitive motion(PM), fine motion(FM) and transitional motion(TM). For PM, a real operator can drive VH in real time for maintenance operation via virtual reality(VR) interactive devices; in this way, the PM can be quickly generated. For FM and TM, their parameterized maintenance motion models are built.2. By using of Hanavan human skeleton structure, a VH real-time driving model is established with a dynamic constraint applied to support personalized human model driving. Then, a complete illumination model for lighting tool is built; and a calibration scheme is designed to measure light source parameters and registration parameters. To map a realistic maintenance process into computer environment, a maintenance process information model is constructed; and a fast, lightweight recording method of maintenance process information is studied and realized.3. In order to improve the driven accuracy in virtual environment(VE), a method is put forward which analyzes the influence factors of virtual human real-time driven accuracy and optimize the factors. A systematical analysis of factors affecting the accuracy is given. The factors can be sorted into hardware factors and software factors. For hardware factors, a noise filtering rule is established based the body joints’ limit angles and the ranges of the joints angles between current frame and previous frame. Then, to compensate these filtered data, a noise compensation model based on Grey System Theory(GST) is built. For software factors, a function is established to describe the driven error during interactive operations. Then, based on the principle of minimum cumulative error, we establish an optimization model with a specified optimization zone and constraints set according to the standard Chinese adult dimensions. Next, the model is solved using genetic algorithm to get the best virtual human segment dimensions matching the real operator. The above methods are verified with the application of some type auto engine operating simulation, and the result shows that the method can improve the driven accuracy effectively.4. An interactive operation modeling method for VH is presented after detailed analysis of interactive assembly and disassembly process. This method deals with interactive operation modeling in scenarios where VH manipulates the product directly, VH manipulates tools, VH manipulates the product using tools, and VH manipulates environment models. To keep the correct relationship between VH and operating objects or tools during constraint solving and navigation processes, an on-line revised method for VH’s posture adjustment is presented. In addition, a user survey is carried out to demonstrate the feasibility and validity of the proposed model and method.5. The semantic-level parameterized models including engineering attributes are created for FM and TM generation. The maintenance motion models include screwing motion, unscrewing motion, tightening motion and untightening motion, knocking motion and inserting motion. Their generation processes are represented. In their generation processes, a virtual human adaptive action model is established on the basis of ergonomic theory to support auto-generating FM and TM.6. To improve the accuracy and efficiency of HFs evaluation for entire maintenance processes, a systematic solution has been proposed. The automatic HFs assessment methods concerning visibility, operation comfort, reachability and synthesized evaluation are presented and realized. For visibility automatic evaluation, a new method is presented. Through projecting operation objects onto view plane, an initial visibility score is calculated according to the projection position and area. Considering that the operation objects may be shaded by other virtual objects during the operation process, a sheltered coefficient is defined to auto-revise the initial score. An improved reachability quantitative evaluation method is presented. Compared to traditional methods, a more detailed operation zone division is implemented. To revise operation space’s influence during operation processes, a barrier-influence coefficient is introduced. Considering the impact of maintenance environment to maintenance operation process, a case study about human factor analysis of radar equipment’s night emergency repair is given to illustrate the effect of lighting conditions to maintenance operation.7. An advanced prototype system VESP-MISA is developed after integrating research achievements. An application in generating VH motions and HFs evaluation for repairing hydraulic motor of container spreader is implemented. Results show that the proposed VH hybrid control method can improve VH motion simulation efficiency. In addition, an on-site survey is conducted to verify the presented HFs auto-evaluating method. The results show that the presented approach can support HFs rapid and accurate evaluation in the early stage of complex equipment design.