Design and implementation of robust visual servoing control of an inverted pendulum with an FPGA-based image co-processor

This paper presents the design and implementation of robust real-time visual servoing control with an FPGA-based image co-processor for a rotary inverted pendulum. The position of the pendulum is measured with a machine vision system. The pendulum used in the proposed system is much shorter than those used in published vision-based pendulum control system studies, which makes the system more difficult to control. The image processing algorithms of the machine vision system are pipelined and implemented on a field programmable gate array (FPGA) device to meet real-time constraints. To enhance robustness to model uncertainty and to attenuate disturbance and sensor noise, the design of the stabilizing controller is formulated as a problem of the mixed H₂/H_∞ control, which is then solved using the linear matrix inequality (LMI) approach. The designed control law is implemented on a digital signal processor (DSP). The effectiveness of the controller and the FPGA-based image co-processor is verified through simulation and experimental studies. The experimental results show that the designed system can robustly control an inverted pendulum in real-time.     

基于三元阵列式MEMS水听器的被动定位系统设计

声纳系统是水下武器装备的重要组成部分,其发展趋向隐蔽性、小型化。文章提出了一种基于小型化三元阵列式微机电系统(MEMS)水听器的被动定位系统。首先,设计了一种三元阵列式MEMS水听器,即在同一芯片上集成三个不同角度偏差的MEMS矢量敏感单元;其次,在充分分析水听器工作原理的基础上建立了阵列式水听器的定位模型,并通过仿真验证了其设计的合理性;最后,以STM32单片机为控制核心设计了阵列式MEMS水听器的信号处理与目标定位系统。这种三元阵列式MEMS水听器在仿真定位中展现了良好的定位精度,充分证明了本系统设计的正确性及实用性。     

Development of a New Robot Controller Architecture with FPGA-Based IC Design for Improved High-Speed Performance

In this paper, a new robot controller architecture is proposed to implement various complex control algorithms for improved high-speed performance. The main thrust of the research is to remove the servo control loop from the digital signal processor (DSP) and implement the high-speed servo loop in a field programmable gate array (FPGA). The main objective of this architecture is to utilize the ultra-high-speed hardwired logic of the FPGA to enhance the overall computational capability and relieve the computational load of the DSP for other tasks. The control algorithm is partitioned into a linear portion and a nonlinear portion. The linear portion with position/velocity feedback represents the major control loop and is implemented in the FPGA. The nonlinear portion acts as dynamic compensation to the linear portion to calculate model-related control gains/parameters, and it is implemented in the DSP. In tandem, with the newly developed control hardware architecture, an FPGA-based motion control integrated circuit (IC) is designed. Experiments are conducted on an industrial robot manipulator to compare the closed-loop performance with this new control architecture and the traditional one, when the same control algorithm is used. The experimental results demonstrate that the proposed new control architecture exhibits much improved motion performance indeed, especially in high-speed motions.     

基于FPGA的液晶控制器设计

介绍了一种基于 FPGA 的集成液晶控制器.系统由显示模块和控制模块组成,显示模块(LEM101)为10 bit 多功能通用型器件,内含看门狗(WDT)/时钟发生器,2 种频率的蜂鸣驱动电路,内置显示RAM,及3-4线串行接口.控制器基于1.5万门 FPGA 芯片(Xilinx XC3S1500),易于扩展和升级.利用 Verilog 语言,在 FPGA 芯片中实现了控制模块的设计,通过 GR-XC3S-1500 开发板验证,本设计完全满足对液晶模块的控制要求,并成功应用于光栅测量显示控制系统中.控制模块由四部分组成:存储、译码、串并转换器、输出控制.文章讨论了设计方法和设计过程,给出了部分 Verilog 代码.此外,本设计还创造性地在电源和 FPGA 芯片间插入低成本元件,满足了液晶上电后,初始化命令的延迟要求,从而节约了 FPGA 的硬件资源.     

FPGA-Based Adaptive Backstepping Sliding-Mode Control for Linear Induction Motor Drive

A field-programmable gate array (FPGA)-based adaptive backstepping sliding-mode controller is proposed to control the mover position of a linear induction motor (LIM) drive to compensate for the uncertainties including the friction force. First, the dynamic model of an indirect field-oriented LIM drive is derived. Next, a backstepping sliding-mode approach is designed to compensate the uncertainties occurring in the motion control system. Moreover, the uncertainties are lumped and the upper bound of the lumped uncertainty is necessary in the design of the backstepping sliding-mode controller. However, the upper bound of the lumped uncertainty is difficult to obtain in advance of practical applications. Therefore, an adaptive law is derived to adapt the value of the lumped uncertainty in real time, and an adaptive backstepping sliding-mode control law is the result. Then, an FPGA chip is adopted to implement the indirect field-oriented mechanism and the developed control algorithms for possible low-cost and high-performance industrial applications. The effectiveness of the proposed control scheme is verified by some experimental results. With the adaptive backstepping sliding-mode controller, the mover position of the FPGA-based LIM drive possesses the advantages of good transient control performance and robustness to uncertainties in the tracking of periodic reference trajectories.     

超声波电动舵机数字舵控系统设计

文章介绍一种超声波电动舵机控制系统的设计与实现方案,该方案以FPGA为控制核心,并采用变速积分PID控制策略来提高系统品质,将舵机控制系统与驱动系统进行一体化设计,从而实现了对超声波电动舵机的一体化控制.实验表明,该超声波舵机系统具有性能稳定、集成度高、精度高等特点,且其性能指标满足使用要求.     

Decentralized nonlinear adaptive control of an HVAC system

This paper presents a new decentralized nonlinear adaptive controller (DNAC) for a heating, ventilating, and air conditioning (HVAC) system capable of maintaining comfortable conditions under varying thermal loads. In this scheme, an HVAC system is considered to be two subsystems and controlled independently. The interactions between the two subsystems are treated as deterministic types of uncertain disturbances and their magnitudes are supposed to be bounded by absolute value. The decentralized nonlinear adaptive controller (DNAC) consists of an inner loop and an outer loop. The inner loop is a single-input fuzzy logic controller (FLC), which is used as the feedback controller to overcome random instant disturbances. The outer loop is a Fourier integral-based control, which is used as the frequency-domain adaptive compensator to overcome steady, lasting uncertain disturbances. The global DNAC controller ensures that the system output vector tracks a desired trajectory vector within the system bandwidth and that the tracking error vector converges uniformly to a zero vector. The simulated experimental results on the HVAC system show that the performance is dramatically improved.     

A Decentralized Model Reference Adaptive Controller for Large-Scale Systems

A decentralized model reference adaptive controller (MRAC) for a class of large-scale systems with unmatched interconnections is developed in this paper. A novel reference model is proposed for the class of large-scale systems considered and a decentralized, full-state feedback adaptive controller is developed for each subsystem of the large-scale system. It is shown that with the proposed decentralized adaptive controller, the states of the subsystems can asymptotically track the desired reference trajectories. To substantiate the performance of the proposed controller, a large web processing line, which mimics most of the features of an industrial web process line, is considered for experimental study. Extensive experiments were conducted with the proposed decentralized adaptive controller and an often used decentralized industrial proportional-integral (PI) controller. A representative sample of the comparative experimental results is shown and discussed     

Micropositioning of a weakly calibrated microassembly system usingcoarse-to-fine visual servoing strategies

This paper presents a novel visual servoing framework for micropositioning in three dimensions for assembly and packaging of hybrid microelectromechanical systems (MEMS). The framework incorporates a supervisory logic-based controller that selects feedback from multiple visual sensors in order to execute a microassembly task. The introduction of a visual sensor array allows the motion of microassembly tasks to be controlled globally with a wide angle view at the beginning of the task. Then a high precision view is used for fine motion control at the end of the task. In addition, a depth-from-focus technique is used to visually servo along the optical axis, providing the ability to perform full three-dimensional (3-D) micropositioning under visual control. The supervisory logic-based controller selects the relevant sensor and tracking strategy to be used at a particular stage in the assembly process, allowing the system to take full advantage of the individual sensor's attributes such as field-of-view, resolution, and depth-of-field. The combination of robust visual tracking and depth estimation within a supervisory control architecture is used to perform high-speed, automatic microinsertions in three dimensions. Experimental results are presented for a micro insertion task performed under this framework in order to demonstrate the feasibility of the approach in high precision assembly of MEMS. Results demonstrate that a relative parts placement repeatable to 2 μm in XY and 10 μm in Z is possible without the use of costly vibration isolation equipment and thermal management systems     

Nonlinear air-to-fuel ratio and engine speed control for hybrid vehicles

Internal combustion spark ignition engine management systems regulate the fuel, spark, and idle air subsystems to achieve sufficient engine performance at acceptable fuel economy and tailpipe emission levels. Engine control units also monitor other engine processes, using a suite of sensors, and periodically check the system actuators' operation to satisfy legislated onboard diagnostics. The majority of production engines regulate the air-to-fuel ratio using a speed-density, or air-flow, control strategy. In this approach, the mass of air drawn into a given cylinder is calculated using the engine speed, manifold absolute pressure, and inlet air temperature. Based on the air mass, appropriate fuel amounts are injected to achieve stoichiometric operation. However, the wide range of operating conditions, inherent induction process nonlinearities, and gradual component degradations due to aging have prompted research into model-based algorithms. In this paper, a nonlinear model-based control strategy will be proposed for simultaneous air-to-fuel ratio control and speed tracking in hybrid electric vehicles. The motivation for engine speed management resides in the integrated control of the engine and a continuously variable transmission for increased efficiency. The proposed backstepping controller uses an observer to reduce the inputs to manifold air mass (e.g., manifold absolute pressure and inlet air temperature) and engine speed. The underlying engine model describes the air intake, fuel injection, and rotational dynamics. For comparison purposes, an existing multisurface sliding mode controller and an integrated speed-density air-to-fuel controller with attached engine speed regulation have been implemented. The performance of each controller is studied using an analytical engine model with representative numerical results presented and discussed to provide insight into the overall performances.     

Control of end-point forces of a multijoint limb by functionalneuromuscular stimulation

A multivariable feedback controller was designed and tested for regulating the magnitude and orientation of the force vector at the end point of a multijoint limb in contact with an isometric load. The force vector was produced by electrical stimulation of muscles. To achieve arbitrary control of end-point force magnitude and orientation, two coupling issues must be dealt with by the control system. First, there is a geometric coupling between the end-point force vector and joint torques. The amplitude and orientation of the force vector depend on the limb geometry. Second, torques at two joints may be coupled due to activation of muscles that cross them (biarticular coupling). To eliminate the geometric coupling, a transformation of controller error from the Cartesian space to the joint space was employed. A multivariable proportional-plus-integral (PI) control law was used to calculate muscle activation based on the transformed controller error. Centralized and decentralized controls were investigated for decoupling the effects of biarticular muscles. The results obtained from cat experiments showed that the magnitude and orientation of the end-point forces of the cat hindlimb could be regulated by this controller. In the presence of strong biarticular coupling, centralized control yielded better performance than decentralized control during transient responses. Both control strategies could decouple the biarticular muscle at steady state. When no biarticular coupling was present, centralized control sometimes performed worse than decentralized control. This is the first step in the simultaneous control of multiple joints by functional neuromuscular stimulation (FNS). The controller has broad potential applications in FNS neural prostheses.     

Steady-State and Dynamic Study of Active Power Filter With Efficient FPGA-Based Control Algorithm

A new approach using field-programmable gate array (FPGA) to implement a fully digital control algorithm of active power filter (APF) is proposed in this paper. This FPGA-based controller integrates the whole signal-processing function of an APF, including synchronous-reference-frame transform, low-pass filter, three-phase phase-locked loop, inverter-current controller, etc. By case studies on the principle, performance, and architecture, these control blocks are implemented in real-time and synthesized into a medium-scale FPGA chip by adopting some useful digital-signal-processing techniques, such as pipelining, folding and strength reduction, with respect to minimization of hardware resource and enhancement of operating frequency. As a result, the whole algorithm needs around 5000 logic elements and can run at synchronous system-clock rates of up to 65 MHz. Experimental results on a laboratory prototype are given to demonstrate performance of the proposed approach during steady-state and dynamic operations.     

基于微程序技术的存储控制器的研究和设计

以一个应用于网络与通讯领域的SOC芯片研发项目为背景,设计了SOC芯片上的存储控制器.该存储控制器基于动态微程序控制技术,用RAM阵列来存储控制字,在SOC芯片初始化时由用户写入控制字,在芯片工作时,也可通过系统总线对RAM阵列进行写操作,使控制字能动态地改变.该结构的存储控制器具有高度的灵活性,可灵活地根据SOC芯片外接的存储器类型进行配置,能够与多种类型的存储器实现无缝连接使用.相比仅适用于某类型存储器的控制器,该存储控制器具有较大的应用优势.     

System identification of power converters with digital control through cross-correlation methods

For digitally controlled switching power converters, on-line system identification can be used to assess the system dynamic responses and stability margins. This paper presents a modified correlation method for system identification of power converters with digital control. By injecting a multiperiod pseudo random binary signal (PRBS) to the control input of a power converter, the system frequency response can be derived by cross-correlation of the input signal and the sensed output signal. Compared to the conventional cross-correlation method, averaging the cross-correlation over multiple periods of the injected PRBS can significantly improve the identification results in the presence of PRBS-induced artifacts, switching and quantization noises. An experimental digitally controlled forward converter with an FPGA-based controller is used to demonstrate accurate and effective identification of the converter control-to-output response.     

The package integration of RF-MEMS switch and control IC for wireless applications

The integration of microelectromechanical systems (MEMS) switch and control integrated circuit (IC) in a single package was developed for use in next-generation portable wireless systems. This packaged radio-frequency (RF) MEMS switch exhibits an insertion loss under -0.4 dB, and isolation greater than -45 dB. This MEMS switch technology has significantly better RF characteristics than conventional PIN diodes or field effect transistor (FET) switches and consumes less power. The RF MEMS switch chip has been integrated with a high voltage charge pump plus control logic chips into a single package to accommodate the low voltage requirements in portable wireless applications. This paper discusses the package assembly process and critical parameters for integration of MEMS devices and bi-complementary metal oxide semiconductor (CMOS) control integrated circuit (IC) into a single package.     

高隔离度宽频段组合式RF-MEMS开关的设计

接触式与电容耦合式两类RF MEMS开关各自在一定的频段内,都具有较高的隔离度,但仍然很难满足微波控制系统中对高隔离度的要求.为了获得全波段高隔离度RF MEMS开关,单元开关很难达到要求,在此目标要求下,提出了组合式RF MEMS开关的设计,分别利用HFSS软件对各单元进行结构参数优化,再将两者集成在一起,得到的组合式RF MEMS开关,这种组合式开关在0～20 GHz时隔离度都高于-60 dB,在(≤5 GHz),隔离度高于-70 dB,这是一般单元开关及其他半导体固态开关所无法企及的,而且,在DC～20 GHz范围内,开关的插入损耗小于-0.20 dB,而且并没因隔离度的提高,牺牲了插入损耗.     

自由场分散式有源声控制系统稳定性分析

分散式反馈有源控制系统通过使用独立的控制单元使系统复杂度与模块数量成线性关系,降低了控制器的设计成本和因设备损坏而导致系统整体失稳的风险,但是会在一定程度上降低系统的稳定性。从控制单元间距和控制器裕量入手,结合性能指数β分析自由场中分散式反馈有源声控制的性能和稳定性。     

FPGA-Based Current Controllers for AC Machine Drives—A Review

The aim of this paper is to present the interest of implementing digital controllers using field-programmable gate array (FPGA) components. To this purpose, a variety of current control techniques, which is applied to alternating current machine drives, is designed and implemented. They consist of on-off current controllers, proportional-integral current controller, and predictive current controller. The quality of the regulated current is significantly improved. It is mainly due to a very important reduction of the execution time delay. Indeed, in all described techniques, the execution time of the designed hardware architectures is only a few microseconds. This time reduction derives directly from the possibility offered by FPGAs to design very powerful dedicated architectures. Numerous experimental results are given in order to illustrate the efficiency of FPGA-based solutions to achieve high-performance control of electrical systems.     

System design for pixel-parallel image processing

A system design for performing low-level image processing tasks in real time is presented. The design is based on large processor-per-pixel arrays implemented using integrated circuit technology. Two integrated circuit architectures are summarized: an associative parallel processor and a parallel processor employing DRAM cells. In both architectures, the layout pitch of one-bit-wide logic is matched to the pitch of memory cells to form high-density processing element arrays. The system design features an efficient control path implementation, providing high processing element array utilization without demanding complex controller hardware. Sequences of array instructions are generated by a host computer before processing begins, then stored in a simple controller. Once processing begins, the host computer initiates stored sequences to perform pixel-parallel operations. A programming framework implemented using the C++ programming language supports application development. A prototype system employs associative parallel processor devices, a controller, and the programming framework. Three sample applications, smoothing and segmentation, median filtering, and optical flow, establish the suitability of the system for real-time image processing