近似直线导引机构可实现无导轨的直线运动，因该类机构结构简单且产生的近似直线精度高，被广泛应用于现代机械领域如数控机床、液压支架、行走机器人等，所以对该类机构综合方法进行深入研究具有理论意义和应用价值。但目前对至少具有二阶以上密切阶的机构综合问题尚未形成统一的机构综合理论和方法。另外，由于实际工程中的随机因素如加工、装配、弹性变形、运动副间隙等的影响，综合所得机构的实际运动输出往往与期望运动输出存在偏差，因此有必要对所得机构进行稳健设计。为此，本文的研究工作如下：

首先，基于瞬时运动几何学理论，采用解析几何法，在已知理想直线点位与机架定铰点位置的条件下，根据四连杆机构拐圆生成技术进行了机构综合公式的推导。通过瞬心位置的求解统一了第一设计变量的选取，利用拐点处连杆曲线与理想直线至少具有三个无限接近点的性质建立了一套直线导引机构通用综合模型，解决具有二阶密切和三阶密切直线导引机构综合问题，机构可以处于一般位形，也可以是特定位形，从而形成了近似直线导引机构综合完整统一的理论体系。

其次，通过设计变量的不同组合可综合得到无穷多的直线机构。本文将解域分析方法应用于直线导引机构的通用综合中，建立以设计变量为坐标轴的直角坐标系，将无穷多直线机构的常规运动学性能如近似直线长度、分支缺陷、机构尺寸、连杆曲线尺寸等表示在有限机构解域内。通过分析有限机构解域，可直观的查看到机构各项性能的分布规律与变化趋势，避免了选取机构的盲目性。

再次，为了在有限机构解域内快速准确的找到满足设计要求的最优稳健机构，本文提出了一种基于解域分析的直线导引机构稳健设计方法。根据实际设计要求对机构施加各类常规运动学约束，满足约束的机构为可行机构，并得到可行解域。为判断可行解域内机构是否满足稳健性能要求，对直线导引机构在受到随机因素影响时的运动输出稳健性提出评价方案，包括连杆点位置偏差与直线度偏差，将以上两项偏差的评价方案量化共同作为衡量机构输出精度的质量特性指标。然后将可行解域内机构离散生成若干个随机样本机构，依据稳健性评价方案判断样本机构的输出精度与常规性能是否满足约束条件，并计算满足条件的概率，若概率值大于规定值，则认为可行机构稳健，并得到可行稳健解域，在可行稳健解域内依据寻优目标寻找到满足机构常规性能要求与稳健性能要求的最优稳健机构解。

最后，采用matlab语言开发了机构通用综合与稳健设计的仿真软件。该软件各项功能通过四个模块实现：机构综合模块可实现具有二阶以上密切直线导引机构和具有三阶密切直线导引机构特定位形的机构综合；常规运动学性能计算模块可计算无穷多机构的常规运动学性能，用户可施加所需的常规约束，生成可行解域；稳健寻优模块可在解域内计算所有机构的稳健性能，通过设定统一的寻优目标，可以在有限的可行稳健解域内显示机构的常规性能分布与稳健性能，并自动找到满足常规性能约束与稳健概率约束的的最优解；图形显示模块可将以上模块的功能以可视化的形式展示给用户，方便用户更快捷高效的获取机构的各项参数。基于本文所提出的通用综合模型以及稳健设计方法，使用开发的仿真软件完成了爬行机器人腿部机构的设计，所得机构的足部轨迹与机构尺寸符合要求，其因噪声因素导致失效的概率仅为0.6%，为满足常规运动学约束和稳健约束的最优稳健解，验证了本文所提通用综合模型与稳健设计方法的正确性与可行性。

The approximate straight-line guidance mechanism can realize the straight-line motion without guide rail. Because of the simple structure of the straight-line mechanism and the high precision of the approximate straight-line, it is of theoretical and practical value to study the synthesis method. However, the unified mechanism synthesis theory and method have not been formed for the mechanism synthesis problem with more than second order close at present. In addition, in practical engineering, the actual motion output of the synthesized mechanism often deviates from the desired motion output due to the influence of random factors such as machining, assembly, elastic deformation and motion pair clearance, so it is necessary to carry out robust design of the resulting mechanism. Therefore, the main research of this paper is as follows:

First, based on the instantaneous motion geometry theory and analytical geometry method, the mechanism synthesis formula is derived according to the generation technology of the inflection circle under the condition that the given ideal straight-line point and the fixed point of the frame. The selection of the first design variable is unified by solving the instantaneous center position. The universal synthesis model of straight-line guidance mechanism is established to solve the synthesis problem of straight-line guidance mechanism with second-order and third-order closeness based on the performance of the inflection point. The specific configuration of third-order close straight-line guidance mechanism is analyzed when the curvature stagnation curve is degraded, and the formula is derived in three cases respectively. A comprehensive and unified theoretical system of linear guidance mechanism has been formed.

Second, infinite straight-line mechanisms can be synthesized by different combinations of design variables. In this paper, the solution region analysis method is applied to the universal synthesis of straight-line guidance mechanism. The conventional kinematics performance such as approximate line length, branch defect, mechanism size and coupler curve size are expressed in the finite mechanism solution region. By analyzed the solution region , the distribution law and change trend of each performance of the mechanism can be seen directly, and the blindness of selecting the mechanism can be avoided.

Third, in order to quickly and accurately find the optimal robust mechanism that meets the design requirements within a finite mechanism solution region, this paper proposes a robust design method for straight-line guidance mechanisms based on solution region analysis. According to the actual design requirements, all kinds of conventional kinematic constraints are applied to the mechanism. The mechanism that satisfies the constraints is a feasible mechanism and the feasible solution region is obtained.

In order to determine whether the mechanism in the feasible solution region meets the robust performance requirements, an evaluation scheme is proposed for the robustness of the motion output of the straight-line guidance mechanism when it is affected by random factors, including the deviation of the linkage point position and the deviation of the straightness. The evaluation scheme of the above two deviations is quantified as the quality characteristic index to measure the output accuracy of the mechanism. Then the feasible solution region is discretized to generate a number of random sample mechanisms. Based on the robustness evaluation scheme to determine whether the output accuracy and conventional performance of the sample mechanisms meet the constraints and calculate the probability of meeting the conditions. The feasible mechanism are considered to be robust if the probability value is greater than the specified value. The feasible robust solution region is obtained. The optimum robust mechanism solution that meets the requirements of the conventional performance and the robust performance requirements is found based on the optimization objective in the feasible robust solution region.

Finally, the simulation software of universal synthesis and robust design of mechanism is developed by using matlab language, which verifies the correctness and feasibility of the proposed universal synthesis model. The functions of the software are realized by four modules : the mechanism synthesis module can realize the mechanism synthesis with the second-order or above close linear guidance mechanism and the specific configuration of the third-order close linear guidance mechanism ; the conventional kinematic performance calculation module can calculate the conventional kinematic performance of infinitely many mechanisms, and the user can apply the required conventional constraints to generate a feasible solution region ; the robust optimization module can calculate the robust performance of all mechanisms in the solution region. By setting a unified optimization goal, the conventional performance distribution and robust performance of the mechanism can be displayed in a limited feasible robust solution region, and the optimal solution satisfying the conventional performance constraints and robust probability constraints can be automatically found. The graphical display module can display the functions of the above modules to the user in a visual form, which is convenient for the user to obtain the parameters of the mechanism more quickly and efficiently. Based on the universal synthesis model and robust design method proposed in this paper, the basic design of the crawling robot leg mechanism is completed by using the developed simulation software. The probability of failure caused by noise factors is only 0.6%, which verifies the correctness and feasibility of the general synthesis model and robust design method proposed in this paper.

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