黑龍江工程學(xué)院本科生畢業(yè)設(shè)計(jì) 1 附 錄 Kinematic Characterization and Optimization of Vehicle Front-suspension Design Based on ADAMS Abstract： To improve the suspension performance and steering stability of light vehicles, we built a kinematic simulation model of a whole independent double-wishbone suspension system by using ADAMS software, created random excitations of the test platforms of respectively the left and the right wheels according to actual running conditions of a vehicle, and explored the changing patterns of the kinematic characteristic parameters in the process of suspension motion. The irrationality of the suspension guiding mechanism design was pointed out through simulation and analysis, and the existent problems of the guiding mechanism were optimized and calculated. The results show that all the front-wheel alignment parameters, including the camber, the toe, the caster and the inclination, only slightly change within corresponding allowable ranges in design before and after optimization. The optimization reduces the variation of the wheel-center distance from 47.01 mm to a change of 8.28 mm within the allowable range of -10 mm to 10 mm, promising an improvement of the vehicle steering stability. The optimization also confines the front-wheel sideways slippage to a much smaller change of 2.23 mm； this helps to greatly reduce the wear of tires and assure the straight running stability of the vehicle. Keywords： vehicle suspension； vehicle steering； riding qualities； independent double-wishbone suspension； kinematic characteristic parameter； wheel-center distance； front-wheel sideways slippage 1 Introduction The function of a suspension system in a vehicle is to transmit all forces and moments exerted on the wheels to the girder frame of the vehicle, smooth the impact passing from the road surface to the vehicle body and damp the impact-caused vibration of the load carrying system. There are many different structures of vehicle suspension, of which the independent double-wishbone suspension is most extensively used. An independent double-wishbone suspension system is usually a group of space RSSR (revolute joint - spherical joint -spherical joint - revolute joint) four-bar linkage mechanisms. Its kinematic relations are complicated, its kinematic visualization is poor, and performance analysis is very difficult. Thus, rational settings of the position parameters of the guiding mechanism are crucial to assuring good performance of the independent double-wishbone suspension. The kinematic characteristics of suspension directly influence the service performance of the vehicle, especially steering stability, ride comfort, turning ease, and tire life. In this paper, we used ADAMS software to build a kinematic analysis model of an 黑龍江工程學(xué)院本科生畢業(yè)設(shè)計(jì) 2 independent double-wishbone suspension, and used the model to calculate and optimize the kinematic characteristic parameters of the suspension mechanism. The optimization results are helpful for improving the kinematic performance of suspension. 2 Modeling independent double-wishbone suspension The performance of a suspension system is reflected by the changes of wheel alignment parameters when the wheels jump. Those changes should be kept within rational ranges to assure the designed vehicle running performance. Considering the symmetry of the left and right wheels of a vehicle, it is appropriate to study only the left or the right half of the suspension system to understand the entire mechanism, excluding the variation of WCD (wheel center distance). We established a model of the left half of an independent double-wishbone suspension system as shown in Figure 1. 3 Kinematic simulation analysis of suspension model Considering the maximum jump height of the front wheel, we positioned the drives on the translational joints between the ground and the test platform, and imposed random displacement excitations on the wheels to simulate the operating conditions of a vehicle running on an uneven road surface. The measured road-roughness data of the left and right wheels were converted into the relationship between time and road roughness at a certain vehicle speed. The spline function CUBSPL in ADAMS was used to fit and generate displacement-time history curves of excitation. The simulation results of the suspension system before optimization are illustrated in Figure 2. The camber angle, the toe angle, the caster angle and the inclination angle change only slightly within the corresponding designed ranges with the wheel jumping distance. This indicates an under-steering behavior together with an automatic returnability, good steering stability and safety in a running process. However, WCD decreases from 1 849.97 mm to 1 896.98 mm and FWSS from 16.48 mm to -6.99 mm, showing remarkable variations of 47.01 mm and 23.47 mm, respectively. Changes so large in WCD and FWSS are adverse to the steering ease and straight-running stability, and cause quick wear, thus reducing tire life. For independent suspensions, the variation of WCD causes side deflection of tires and then impairs steering stability through the lateral force input. Especially when the right and the left rolling wheels deviate in the same direction, the WCD-caused lateral forces on the right and the left sides cannot be offset and thus make steering unstable. Therefore, WCD variation should be kept minimum, and is required in suspension design to be within the range from -10 mm to 10 mm when wheels jump. It is obvious that the WCD of non-optimized structure of the suspension system goes beyond this range. The structure needs modifying to suppress FWSS and the change of WCD with the wheel jumping distance. ADMAS software is a strong tool for parameter optimization and analysis. It creates a parameterization model by simulating with different values of model design variables, and then analyzes the parameterization based on the returned simulation results and the final 黑龍江工程學(xué)院本科生畢業(yè)設(shè)計(jì) 3 optimization calculation of all parameters. During optimization, the program automatically adjusts design variables to obtain a minimum objective function 8-10. To reduce tire wear and improve steering stability, the Table 1 Values of camber angle , toe angle , caster angle and inclination angle before and after optimization Table 1 The data tables of optimize the results 4 Conclusions The whole kinematic simulation model of an independent double-wishbone suspension system built by using ADAMS software with the left and the right suspension parts under random excitations can improve the calculation precision by addressing the mutual impacts of kinematic characteristic parameters of the left and the right suspension parts under random excitations. The optimization can overcome the problem of the too large variation of WCD and overly large FWSS with the wheel jumping distance. The kinematic characteristic parameters of the suspension system reach an ideal range, demonstrating that the optimization protocol is feasible. From a practical perspective, the optimization is expected to reduce tire wear, and remarkably improve suspension performance and vehicle steering stability. Figure 1 simple picture of suspension 黑龍江工程學(xué)院本科生畢業(yè)設(shè)計(jì) 4 Figure 2 Curve with the parameters of the suspension 黑龍江工程學(xué)院本科生畢業(yè)設(shè)計(jì) 5 基于 ADAMS 前懸架優(yōu)化設(shè)計(jì) 摘要：為了提高輕型車輛性能和行駛穩(wěn)定，我們使用 ADAMS軟件建立一個(gè)獨(dú)立雙橫臂懸架系統(tǒng)運(yùn)動(dòng)仿真模型，并建立隨機(jī)激勵(lì)的測(cè)試平臺(tái)，根據(jù)車輛實(shí)際運(yùn)行條件，探討懸架的運(yùn)動(dòng)學(xué)特征參數(shù)的變化。通過仿真和優(yōu)化的可以對(duì)懸架設(shè)計(jì)進(jìn)行相關(guān)的指導(dǎo)。試驗(yàn)表明，所有的前輪定 位參數(shù)，包括前輪前束角，主銷內(nèi)傾角，注銷后傾角，前輪外傾角都可以得到優(yōu)化。例如只要在仿真前或后改變一個(gè)很小的量，車輪中心距就可以從 mm01.47 減小到許用范圍 mm1010 從而改善了車輛的操縱穩(wěn)定性。此外還優(yōu)化了前輪側(cè)向滑動(dòng)量，使之減小到 mm23.2 ，更有助于減少輪胎磨損，保證車輛的行駛穩(wěn)定性。 關(guān)鍵詞：汽車懸架 ； 車輛轉(zhuǎn)向 ； 駕駛 性能 ； 獨(dú)立雙橫臂懸架 ； 運(yùn)動(dòng)學(xué)特征參數(shù) ； 輪中心距 ； 前輪側(cè)向滑移 1 簡(jiǎn)介 汽車懸架的功用時(shí)承受來自地面?zhèn)髦淋嚿淼臎_擊，保證車輛在行駛過程中的操縱穩(wěn)定性和平順性的系統(tǒng)。懸架有很多種類，其中雙橫臂獨(dú)立懸架時(shí)應(yīng)用最為廣泛的一種。獨(dú)立的雙橫臂懸掛系統(tǒng)通常是一組空間四連桿機(jī)制。其運(yùn)動(dòng)關(guān)系復(fù)雜，性能分析是非常困難。因此，合理的設(shè)置參數(shù)對(duì)指導(dǎo)其設(shè)計(jì)是至關(guān)重要的。為確保汽車具有良好的性能，特別是操縱穩(wěn)定性，乘坐舒適，轉(zhuǎn)向緩和，輪胎壽命。因此對(duì)懸架的設(shè)計(jì)時(shí)非常重要的。在本文中，我們使用 ADAMS軟件建立一個(gè)獨(dú)立的雙橫臂懸掛系統(tǒng)的運(yùn)動(dòng)學(xué)分析模型，并利用該模型計(jì)算和優(yōu)化的運(yùn)動(dòng)特征參數(shù)。優(yōu)化的結(jié)果，有助于知道我們對(duì)懸架的設(shè)計(jì)。 2 獨(dú)立雙橫臂懸架的建模 當(dāng)車輪跳東時(shí)懸掛系統(tǒng)的性能受到車輪定位參數(shù)變化的影響。這些變化應(yīng)保持在合理的范圍，以保證所設(shè)計(jì)的車輛行駛性能。考慮到獨(dú)立懸架的左，右車輪是對(duì)稱的，因此我們只要研究左側(cè)或右側(cè) 的懸掛系統(tǒng)，就可以了解整個(gè)懸架系統(tǒng)，但不包括車輪中心的距離的變化 。我們建立一個(gè)如圖 1所示的模型，此模型為獨(dú)立雙橫臂懸掛系統(tǒng)的左側(cè)系統(tǒng)。 3 懸架模型運(yùn)動(dòng)學(xué)仿真分析 考慮到前輪最大的跳動(dòng)高度，我們?cè)诘孛婧蜏y(cè)試平臺(tái)放置一個(gè) 上、下運(yùn)動(dòng)的驅(qū)動(dòng)幅，并加上車輛在路面上實(shí)際運(yùn)動(dòng)時(shí)上、下運(yùn)動(dòng)的關(guān)系加上隨機(jī)激勵(lì)。 實(shí)測(cè)的道路粗糙度數(shù)據(jù)是根據(jù)左，右車輪在一定時(shí)間內(nèi)、一定車速和