A pneumatic parallel platform driven by an air cylinder and three circumambient pneumatic muscles was considered. Firstly, a mathematical model of the pneumatic servo system was developed for the MIMO nonlinear model-...A pneumatic parallel platform driven by an air cylinder and three circumambient pneumatic muscles was considered. Firstly, a mathematical model of the pneumatic servo system was developed for the MIMO nonlinear model-based controller designed. The pneumatic muscles were controlled by three proportional position valves, and the air cylinder was controlled by a proportional pressure valve. As the forward kinematics of this structure had no analytical solution, the control strategy should be designed in joint space. A cross-coupling integral adaptive robust controller(CCIARC) which combined cross-coupling control strategy and traditional adaptive robust control(ARC) theory was developed by back-stepping method to accomplish trajectory tracking control of the parallel platform. The cross-coupling part of the controller stabilized the length error in joint space as well as the synchronization error, and the adaptive robust control part attenuated the adverse effects of modelling error and disturbance. The force character of the pneumatic muscles was difficult to model precisely, so the on-line recursive least square estimation(RLSE) method was employed to modify the model compensation. The projector mapping method was used to condition the RLSE algorithm to bound the parameters estimated. An integral feedback part was added to the traditional robust function to reduce the negative influence of the slow time-varying characteristic of pneumatic muscles and enhance the ability of trajectory tracking. The stability of the controller designed was proved through Laypunov's theory. Various contrast controllers were designed to testify the newly designed components of the CCIARC. Extensive experiments were conducted to illustrate the performance of the controller.展开更多
A new normalized least mean square(NLMS) adaptive filter is first derived from a cost function, which incorporates the conventional one of the NLMS with a minimum-disturbance(MD)constraint. A variable regularization f...A new normalized least mean square(NLMS) adaptive filter is first derived from a cost function, which incorporates the conventional one of the NLMS with a minimum-disturbance(MD)constraint. A variable regularization factor(RF) is then employed to control the contribution made by the MD constraint in the cost function. Analysis results show that the RF can be taken as a combination of the step size and regularization parameter in the conventional NLMS. This implies that these parameters can be jointly controlled by simply tuning the RF as the proposed algorithm does. It also demonstrates that the RF can accelerate the convergence rate of the proposed algorithm and its optimal value can be obtained by minimizing the squared noise-free posteriori error. A method for automatically determining the value of the RF is also presented, which is free of any prior knowledge of the noise. While simulation results verify the analytical ones, it is also illustrated that the performance of the proposed algorithm is superior to the state-of-art ones in both the steady-state misalignment and the convergence rate. A novel algorithm is proposed to solve some problems. Simulation results show the effectiveness of the proposed algorithm.展开更多
A new variable step-size algorithm for a second-order lattice form structure adaptive infinite impulse response （IIR） notch filter to detection and estimation frequency of sinusoids in Gaussian noises is proposed. U...A new variable step-size algorithm for a second-order lattice form structure adaptive infinite impulse response （IIR） notch filter to detection and estimation frequency of sinusoids in Gaussian noises is proposed. Utilizing least square kurtosis of output signals as a cost function, the new gradient-based algorithm to update frequency of the adaptive IIR notch filter and the new variable step-size algorithm are given. The computer simulation results show that the proposed algorithm has better ability in suppressing colored Gaussian noises and better accuracy in estimating parameters at low SNR than previous algorithms.展开更多
电力电子发电装备输出阻抗在宽频带范围内存在负电阻特性,在接入弱电网时,发电装备与电网阻抗交互作用,易诱发新能源并网系统宽频带振荡现象。为解决该问题,提出在公共耦合点(point of common coupling,PCC)并联一个基于自适应虚拟阻抗...电力电子发电装备输出阻抗在宽频带范围内存在负电阻特性,在接入弱电网时,发电装备与电网阻抗交互作用,易诱发新能源并网系统宽频带振荡现象。为解决该问题,提出在公共耦合点(point of common coupling,PCC)并联一个基于自适应虚拟阻抗控制的自适应阻抗适配器,在不同工况下自适应增强系统的阻尼,提高系统的稳定性,实现新能源并网系统的宽频带振荡抑制。所提方法无需复杂的虚拟阻抗设计,通过引入PCC点电压峰值变化量控制支路,即可得到自适应虚拟电阻,有效提高了阻抗适配器的灵活性与适应性。建立了考虑频率耦合的自适应阻抗适配器序导纳模型,对比分析了并入自适应阻抗适配器前后新能源并网系统的导纳特性,并入自适应阻抗适配器后,新能源并网系统的负阻性区域显著减少。基于所建的导纳模型,采用广义奈奎斯特稳定判据对系统稳定性进行了分析,分析结果表明自适应阻抗适配器有效提升了新能源并网系统在弱电网下的稳定性。最后,仿真验证了理论分析的准确性和所提基于自适应虚拟电阻控制的自适应阻抗适配器的有效性。展开更多
压环是爆炸成型弹丸(Explosively Formed Projectile,EFP)装药结构中紧固装药和药型罩不可缺少的部件。为研究其在爆炸驱动过程中对药型罩形成EFP特征的影响,选取典型球缺型紫铜药型罩基准装药结构,采用有限元分析软件的拉格朗日、任意...压环是爆炸成型弹丸(Explosively Formed Projectile,EFP)装药结构中紧固装药和药型罩不可缺少的部件。为研究其在爆炸驱动过程中对药型罩形成EFP特征的影响,选取典型球缺型紫铜药型罩基准装药结构,采用有限元分析软件的拉格朗日、任意拉格朗日-欧拉、光滑粒子流法(Smooth Particle Hydrodynamics,SPH)及有限元法(Finite Element Method,FEM)-SPH自适应耦合等算法分别建模和仿真计算,对各算法计算获得的EFP速度和形态特征与脉冲X光摄影拍摄的EFP图像进行对比,采用FEM-SPH算法获得高精度的EFP成型仿真结果。针对该基准装药结构,在压环与药型罩质量比M_(R)/M_(L)≤0.2范围,进行矩形及非矩形压环参数(如轴向、径向厚度及截面形状)和材料对EFP初速、质量转换比、长径比和气动特性(密实度及迎风面积)参数影响的仿真计算。研究结果表明:矩形截面压环的轴向、径向厚度及材料参数对EFP初速影响在3%以内;对EFP质量转换比呈递减趋势(最大可降低12.6%);对EFP长径比呈递减趋势(最大可降低19.2%);密实度呈递增趋势,钢环较无压环,EFP的密实度提高32.6%;迎风面积呈递减趋势。以上结果表明考虑压环有利于EFP翻转成型和形成更密实的杆式EFP,并减小其迎风阻力。所得研究结果可为EFP装药结构的优化设计提供指导。展开更多
基金Project(51375430)supported by the National Natural Science Foundation of China
文摘A pneumatic parallel platform driven by an air cylinder and three circumambient pneumatic muscles was considered. Firstly, a mathematical model of the pneumatic servo system was developed for the MIMO nonlinear model-based controller designed. The pneumatic muscles were controlled by three proportional position valves, and the air cylinder was controlled by a proportional pressure valve. As the forward kinematics of this structure had no analytical solution, the control strategy should be designed in joint space. A cross-coupling integral adaptive robust controller(CCIARC) which combined cross-coupling control strategy and traditional adaptive robust control(ARC) theory was developed by back-stepping method to accomplish trajectory tracking control of the parallel platform. The cross-coupling part of the controller stabilized the length error in joint space as well as the synchronization error, and the adaptive robust control part attenuated the adverse effects of modelling error and disturbance. The force character of the pneumatic muscles was difficult to model precisely, so the on-line recursive least square estimation(RLSE) method was employed to modify the model compensation. The projector mapping method was used to condition the RLSE algorithm to bound the parameters estimated. An integral feedback part was added to the traditional robust function to reduce the negative influence of the slow time-varying characteristic of pneumatic muscles and enhance the ability of trajectory tracking. The stability of the controller designed was proved through Laypunov's theory. Various contrast controllers were designed to testify the newly designed components of the CCIARC. Extensive experiments were conducted to illustrate the performance of the controller.
基金supported by the National Natural Science Foundation of China(61571131 11604055)
文摘A new normalized least mean square(NLMS) adaptive filter is first derived from a cost function, which incorporates the conventional one of the NLMS with a minimum-disturbance(MD)constraint. A variable regularization factor(RF) is then employed to control the contribution made by the MD constraint in the cost function. Analysis results show that the RF can be taken as a combination of the step size and regularization parameter in the conventional NLMS. This implies that these parameters can be jointly controlled by simply tuning the RF as the proposed algorithm does. It also demonstrates that the RF can accelerate the convergence rate of the proposed algorithm and its optimal value can be obtained by minimizing the squared noise-free posteriori error. A method for automatically determining the value of the RF is also presented, which is free of any prior knowledge of the noise. While simulation results verify the analytical ones, it is also illustrated that the performance of the proposed algorithm is superior to the state-of-art ones in both the steady-state misalignment and the convergence rate. A novel algorithm is proposed to solve some problems. Simulation results show the effectiveness of the proposed algorithm.
文摘A new variable step-size algorithm for a second-order lattice form structure adaptive infinite impulse response （IIR） notch filter to detection and estimation frequency of sinusoids in Gaussian noises is proposed. Utilizing least square kurtosis of output signals as a cost function, the new gradient-based algorithm to update frequency of the adaptive IIR notch filter and the new variable step-size algorithm are given. The computer simulation results show that the proposed algorithm has better ability in suppressing colored Gaussian noises and better accuracy in estimating parameters at low SNR than previous algorithms.
文摘电力电子发电装备输出阻抗在宽频带范围内存在负电阻特性,在接入弱电网时,发电装备与电网阻抗交互作用,易诱发新能源并网系统宽频带振荡现象。为解决该问题,提出在公共耦合点(point of common coupling,PCC)并联一个基于自适应虚拟阻抗控制的自适应阻抗适配器,在不同工况下自适应增强系统的阻尼,提高系统的稳定性,实现新能源并网系统的宽频带振荡抑制。所提方法无需复杂的虚拟阻抗设计,通过引入PCC点电压峰值变化量控制支路,即可得到自适应虚拟电阻,有效提高了阻抗适配器的灵活性与适应性。建立了考虑频率耦合的自适应阻抗适配器序导纳模型,对比分析了并入自适应阻抗适配器前后新能源并网系统的导纳特性,并入自适应阻抗适配器后,新能源并网系统的负阻性区域显著减少。基于所建的导纳模型,采用广义奈奎斯特稳定判据对系统稳定性进行了分析,分析结果表明自适应阻抗适配器有效提升了新能源并网系统在弱电网下的稳定性。最后,仿真验证了理论分析的准确性和所提基于自适应虚拟电阻控制的自适应阻抗适配器的有效性。
文摘压环是爆炸成型弹丸(Explosively Formed Projectile,EFP)装药结构中紧固装药和药型罩不可缺少的部件。为研究其在爆炸驱动过程中对药型罩形成EFP特征的影响,选取典型球缺型紫铜药型罩基准装药结构,采用有限元分析软件的拉格朗日、任意拉格朗日-欧拉、光滑粒子流法(Smooth Particle Hydrodynamics,SPH)及有限元法(Finite Element Method,FEM)-SPH自适应耦合等算法分别建模和仿真计算,对各算法计算获得的EFP速度和形态特征与脉冲X光摄影拍摄的EFP图像进行对比,采用FEM-SPH算法获得高精度的EFP成型仿真结果。针对该基准装药结构,在压环与药型罩质量比M_(R)/M_(L)≤0.2范围,进行矩形及非矩形压环参数(如轴向、径向厚度及截面形状)和材料对EFP初速、质量转换比、长径比和气动特性(密实度及迎风面积)参数影响的仿真计算。研究结果表明:矩形截面压环的轴向、径向厚度及材料参数对EFP初速影响在3%以内;对EFP质量转换比呈递减趋势(最大可降低12.6%);对EFP长径比呈递减趋势(最大可降低19.2%);密实度呈递增趋势,钢环较无压环,EFP的密实度提高32.6%;迎风面积呈递减趋势。以上结果表明考虑压环有利于EFP翻转成型和形成更密实的杆式EFP,并减小其迎风阻力。所得研究结果可为EFP装药结构的优化设计提供指导。
