QNX Real-time Operating System Research Articles

A High Speed Redundant IO Bus for Energy Power Controller System

This paper designs and implements a High Speed Redundant IO Bus for Energy Power Controller System. The physical layer adopts multi-point low-voltage differential signal standard. This bus has the characteristics of high real-time, high throughput and easy expansion. The controller communicates with IO module by A/B bus alternately, monitors link status in real time and collects IO module data. Non real time slots can be used to control non real time messages for IO modules such as time synchronizing and memory monitoring. The controller ARM core runs QNX real-time operating system, and transmits the message needed to communicate with IO modules to the FPGA through DMA. After receiving the message, the FPGA parses the message and automatically fills in the CRC check code and frame end flag at the end of the message. When the FPGA receives the data feedback from the IO module, it performs CRC verification. If the verification passes, it fills the corresponding module receiving buffer. Otherwise, it fills the CRC verification error flag in the register of the corresponding IO module to reduce the load of the arm core.

Real-time compliance control of an assistive joint using QNX operating system

An assistive robot is a novel service robot, playing an important role in the society. For instance, it can amplify human power not only for the elderly and disabled to recover/rehabilitate their lost/impaired musculoskeletal functions but also for healthy people to perform tasks requiring large forces. Consequently, it is required to consider both accurate position control and human safety, which is the compliance. This paper deals with the robot control compliance problem based on the QNX real-time operating system. Firstly, the mechanical structure of a compliant joint on the assistive robot is designed using Solidworks. Then the parameters of the assistive robot system are identified. The software of robot control includes data acquisition and processing, and control to meet the compliance requirement of the joint control. Finally, a Hogan impedance control experiment is carried out. The experimental results prove the effectiveness of the method proposed.

An Unmanned Rotorcraft System with Embedded Design

In this paper, we present the systematic design and implementation of quick prototype design and hardware-in-the-loop real-time test of the embedded control system of Unmanned Rotorcraft. The control law is of backstepping type, the sensory system consists of a marker-based vision system outside the helicopter in radio connection with the embedded controller and a 3D inertial measurement unit (IMU) on the helicopter. Extended Kalman filters solve the state estimation problem. Brushless DC motors serve as actuators. For quick prototype design of the embedded controller MATLAB, Simulink, Real-Time Workshop and the MPC555 Target Compiler were used. More specifically, the onboard hardware system is designed to fulfill the image processing requirements by using the commercial off-the-shelf products. Real-time vision software is developed, which is running on the real-time operating system QNX.

Dynamic Clamp Conductance Injection Software Based on the QNX Real Time Operating System with Error Control and an Implicit Integration Method

Dynamic clamp or conductance injection is an electrophysiological method that uses a real-time interface between living cells and a computer to simulate conductance changes in the membrane. To date, the numerical integration methods used for this purpose have been explicit. These methods have an upper bound for the length of the step size when the method becomes numerically unstable. This becomes a practical problem particularly when injecting fast voltage-dependent conductances. Here, we improve the numerical integration of the equations underlying such conductances by implementing an implicit method (Iserles & Norsett, IMA J. Num. Anal. 10:463, 1990), suited for stiff equations. Specifically, this is an A- and L-stable diagonal implicit Runge-Kutta method, which can exploit information about the membrane potential sampled at subintervals of the current update period, which we demonstrate can greatly improve the accuracy and stability of the injected conductance. Furthermore, the integration method let us implement real-time error monitoring.We have built our implementation of this on the QNX microkernel real-time operating system, widely used for high-speed mission-critical real-time applications in industry. Its flexibility and reliability in timing, interrupt control and processor scheduling in multiprocessor systems, and its microkernel architecture (which frees up more CPU time than other comparable systems for running the model), make it an ideal platform for more complex integration methods such as the one we describe. The here offered prospect of an improved accuracy and stability of the conductance injection technique, opens up for analyzing membranes with faster channels than was previously possible.

QNX and Simulink-Based Control Platform for HIT/DLR II Robot Hand

This paper presented a control platform for HIT/DLR II robot hand, which is based on QNX real-time operating system and Simulink software. The platform accelerates the development of robot hand control algorithm and hardware-in-the-loop (HIL) testing using Model-Based Design techniques of MATLAB Simulink. This paper also validated the performance of the platform by using two applications: single-finger position control and grasp application.

NONLINEAR MODEL PREDICTIVE CONTROL OF ROBOTS, CRANES AND VEHICLES

The main goal of the paper is to show that nonlinear model based predictive control is an effective alternative method for controlling uncertain nonlinear underactuated systems satisfying real time expectations where uncertainty is caused by friction and disturbance. The paper presents control algorithms for a two degree of freedom robot and for two underactuated systems, the small size model of a planar crane and a weeled mobile robot, which are based on nonlinear model predictive control. The continuous time dynamic model has been discretized and the finite dimensional optimization problem is solved by conjugate gradient technique in every horizon. Extended Kalman filter is used for state and disturbance estimation. For the crane the initial approximation of the control sequence within the actual horizon is determined by using the flatness properties. For development purposes a multiprocessor system has been elaborated where the control algorithm is running under QNX real-time operating system. The paper also presents experimental results that demonstrate the applicability of the proposed algorithms under real time conditions.

Control system for the waterjet cutting Machine

This paper addresses the field of factory automation within the scope of machine control. It presents the control system for a waterjet cutting machine. It involves a PC based computer numerical control (CNC) controller that has been built on a QNX real-time (RT) operating system platform. Microsoft Windows, which is a commonly accepted graphical user interface environment, serves as a human machine interface (HMI) front-end. The CNC controller and the HMI are interconnected by the Ethernet TCP/IP link. The control system is flexible and modular. It supports CAD/CAM and a network link to the office-level of factory automation. The application is thoroughly presented with the highlight on RT features; the QNX RT operating system is analyzed in detail. Moreover, Ethernet TCP/IP technology for the use in a networked automated factory is also put in the foreground.

Reconfigurable distributed real-time processing for multi-robot control: Design, implementation and experimentation

Sophisticated robotic applications require systems to be reconfigurable at the system level. Aiming at this requirement, this paper presents the design and implementation of a software architecture for a reconfigurable real-time multi-processing system for multi-robot control. The system is partitioned into loosely coupled function units and the data modules manipulated by the function units. Modularized and unified structures of the sub-controllers and controller processes are designed and constructed. All the controller processes run autonomously and intra-sub-controller information exchange is realized by shared data modules that serve as a data repository in the sub-controller. The dynamic data-management processes are responsible for data exchange among sub-controllers and across the computer network. Among sub-controllers there is no explicit temporal synchronization and the data dependencies are maintained by using datum-based synchronization. The hardware driver is constructed as a two-layered system to facilitate adaptation to various robotic hardware systems. A series of effective schemes for software fault detection, fault anticipation and fault termination are accomplished to improve run-time safety. The system is implemented cost-effectively on a QNX real-time operating system (RTOS) based system with a complete PC architecture, and experimentally validated successfully on an experimental dual-arm test-bed. The results indicate that the architectural design and implementation are well suited for advanced application tasks.

Real-time data acquisition and control system for the 349-pixel TACTIC atmospheric Cherenkov imaging telescope

An interrupt-based multinode data acquisition and control system has been developed for the imaging element of the TACTIC γ-ray telescope. The system which has been designed around a 3-node network of PCs running the QNX real-time operating system, provides single-point control with elaborate GUI facilities for operating the multi-pixel camera of the telescope. In addition to acquiring data from the 349-pixel photomultiplier tube based imaging camera in real time, the system also provides continuous monitoring and control of several vital parameters of the telescope for ensuring the quality of the data. The paper describes the salient features of the hardware and software of the data acquisition and control system of the telescope.

Real-Time Active Control of Vibrations in a Flexible Beam Using Piezoelectric Transducers

This paper discusses the selection process for piezoelectric transducers (PZT) used as actuator elements for suppressing vibrations in a flexible beam system. A model for a clamped-free cantilevered beam is developed. The effects of changing physical parameters such as thickness of the piezoelectric ceramic, the optimum location of the PZT actuator, and the length of the PZT are studied based on the singular value decomposition of the controllability Grammian of the resulting system. A real-time experiment using the beam system with an active damping controller is implemented under the QNX real-time operating system. Simulation and experimental results show that applying a conventional controller to the system results in considerable vibration attenuation of the dominant modes.

Multifunctional walking quadruped

A multifunctional 4 legged walking machine that is being developed in the Robotics Research Centre (NTU) is described. The major factors influencing the design requirements include minimisation of the weight of the machine and maximisation of workspace of the legs. The designed walking machine can adopt a variety of configurations, such as insect, mammalian, reptile or human. The device is invertable (i.e. can turn over). It can use its legs as manipulators, hence it can perform basic pick-and-place functions. A control system was built using the QNX real-time operating system platform. The software was designed using the client-server approach.