本文關(guān)鍵詞： 多體動力學(xué) 彈性接觸 被動行走 穩(wěn)定性 吸引域　出處：《清華大學(xué)》2013年博士論文　論文類型：學(xué)位論文

【摘要】：被動行走是雙足仿生行走的新概念。相比于傳統(tǒng)的雙足行走，其優(yōu)點為能量消耗率很低。被動行走的仿真研究一般采用倒立擺模型假設(shè)，認(rèn)為支撐足與地面鉸接，足在地面上不發(fā)生彈起以及相對滑動。這種簡化模型忽略了足與地面接觸的過程。在各種多體系統(tǒng)中，碰撞與接觸問題對于系統(tǒng)的動力學(xué)行為與穩(wěn)定性有很重要的影響，實際的被動行走多體系統(tǒng)中足與地面接觸也是行走過程的重要環(huán)節(jié)。 為研究上述接觸過程對行走的影響，本文首先建立了考慮足與地面彈性接觸的二維被動行走模型，利用Hertz接觸（彈簧阻尼）模型以及經(jīng)過改進的Coulomb摩擦模型分別描述足與地面的法向接觸力與切向摩擦力。通過動力學(xué)仿真，在尋找到周期行走步態(tài)的同時，得到了行走過程的接觸力變化。通過改變模型的接觸剛度系數(shù)、阻尼系數(shù)以及摩擦系數(shù)，發(fā)現(xiàn)接觸阻尼系數(shù)與摩擦系數(shù)對于行走步態(tài)基本無影響，接觸剛度系數(shù)對于行走的步態(tài)影響最大。接觸剛度系數(shù)越大，，行走的平均速度和碰撞力峰值越大。 通過增加仿真模型的斜面傾角，可得到單步周期、二步周期、多步周期等周期加倍的行走結(jié)果，這與Gacia等人的倒立擺模型結(jié)果類似。改變模型參數(shù)及接觸參數(shù)，可得到參數(shù)對步態(tài)分岔點的影響。仿真結(jié)果表明接觸剛度系數(shù)越大，步態(tài)分岔發(fā)生的傾角越小，其它接觸參數(shù)對分岔點沒有影響。 進一步利用Floquet乘子以及胞映射方法對行走的穩(wěn)定性研究。通過簡單假設(shè)使動力學(xué)系統(tǒng)的狀態(tài)空間降維，得到了3維胞空間下的被動行走吸引域。通過改變接觸參數(shù)，發(fā)現(xiàn)接觸剛度系數(shù)與接觸阻尼系數(shù)對吸引域大小沒有影響；摩擦系數(shù)越大，行走的吸引域越大。這說明摩擦力是考慮彈性接觸的被動行走穩(wěn)定性的決定因素。 為驗證仿真模型結(jié)果，建立了含有測試系統(tǒng)的簡單直腿被動行走實驗?zāi)Ｐ�。利用陀螺儀測量雙腿擺角，利用薄膜力傳感器測量足地接觸的法向力。在不同行走介質(zhì)上測試的結(jié)果，說明了摩擦力對行走穩(wěn)定性的決定作用。利用測試得到的行走步態(tài)以及接觸法向力曲線，與仿真模型結(jié)果進行了對比，二者吻合較好。這說明考慮足與地面彈性接觸的被動行走模型是更加接近真實物理模型的。
[Abstract]:Passive walking is a new concept of double foot bionic walking biped walking. Compared to the traditional, the utility model has the advantages of energy consumption rate is very low. Simulation Research on passive walking generally use the inverted pendulum model hypothesis, that the foot support is hinged with the ground, the foot does not occur on the ground bounce and relative sliding. This simplified model ignores the process of full contact with the ground. In a variety of multibody systems, collision and contact problem has an important effect on the dynamic behavior and stability of the system, the actual passive walking multi-body system midleg in contact with the ground. Walking is an important part of the process
For the process of the contact of walking effect, this paper consider the two-dimensional elastic contact of the foot and the ground passive walking model, using Hertz (contact spring damping) model and the Coulomb friction model is improved through the foot and the ground respectively describe the normal contact force and tangential friction force. Through dynamic simulation, looking into cycle walking at the same time, the contact force of the walking process changes. By changing the model of contact stiffness coefficient, damping coefficient, friction coefficient, damping coefficient and friction coefficient of contact found for gait has no effect, the contact stiffness coefficient has the greatest impact on the walking gait. The contact stiffness coefficient increases, the speed of walking the average and maximum impact force is greater.
The slant angle increase simulation model, can be obtained by single step cycle, two step cycle, the double step walking cycle cycle, and the Gacia's inverted pendulum model. Similar results change the model parameters and contact parameters, can get the influence of parameters on the gait of the bifurcation point. The simulation results show that the contact stiffness coefficient increases angle, gait bifurcation is small and the other contact parameters have no effect on the bifurcation point.
Study on the stability of the further use of Floquet multiplier and cell mapping method of walking. The state space dynamics system through simple hypothesis reduction, the passive walking 3 dimensional cellular space under the domain of attraction. By changing the contact parameters, found that the contact stiffness coefficient and contact damping coefficient has no effect on the size of the domain of attraction; friction coefficient large, walking more. This shows that the domain of attraction of the friction force is the decisive factor of passive walking stability considering elastic contact.
In order to verify the results of simulation models is established, containing the test system has the advantages of simple passive walking straight leg experimental model. Using the gyroscope to measure the swing angle of the legs, foot contact with film force sensor to measure the normal force. Test in different travel medium results illustrate the decisive role on the stability of walking friction. Using gait test get and contact normal force curve, compared with the simulation results of the model, two are in good agreement. This indicates that considering passive walking model of foot and ground elastic contact is more close to the real physical model.

【學(xué)位授予單位】：清華大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2013
【分類號】：TH113;TP242

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本文編號：1537707