Analog-to-Digital Converter (A/D)
An electrical circuit used to convert analog signals to a time series of digital numbers.
(See Analog Signal) back to top Analog Signal
A voltage or current varying with changes in a real physical quantity. For example, the output of an accelerometer is a voltage analogous the acceleration of the accelerometer is measuring. back to top Control Loop
A control system functions by feeding back a sensor signal measuring the state of the system at this moment and comparing it to the desired state of the system. The deviation from the desired state (the error) is used to compute a new control input to the system. The path of the signals form a loop in a block diagram and thus the term “control loop.” Such a diagram is quite common in graphically programmed real time control systems, such as the ReaLINK-CP-1002, or the RT-300 systems back to top Controller Prototyping
The use of simulation to quickly test how a controller will function in the field. Through the use of a block-diagram programming environment, a simulated controller can be connected to the real hardware. Also referred to as rapid-controller prototyping and embedded-controller prototyping. XANALOG’s Model RT-300 which runs XANALOG’s nonlinear simulation language, NL-SIM, can be used for rapid controller prototyping. In addition, for running SIMULINK models in real-time, XANALOG provides the Model ReaLINK-CP-1002. For example, with XANALOG’s controller-prototyping systems, control engineers designing and testing automobile-engine, fuel-injection controllers can easily make changes through a block-diagram programming environment rather than enduring the laborious process of using C code or assembly code. This process cuts development and testing cycles of the fuel-injection controller by finding errors early in the development process, when they are less costly to correct. back to top Difficult Loop
A control loop for a system that is difficult to control. For example, a common controller, such as a PID, may be unable to control a system with a long time lapse between when a correcting input is applied and the response is measured. (See Control Loop) To accomplish control in such a situation a more sophisticated controller such as a model-based controller is needed. See the rendering below: showing a boiler and measuring point. back to top Digital-to-Analog Converter (D/A)
An electrical circuit used to convert a series of digital numbers to an analog voltage. (See Analog and Analog-to-Digital Converter (A/D)) back to top Digitized Signals
An analog current or voltage passed to an analog-to-digital converter (A/D) to convert a series of numbers in a digital computer. Similarly the output of a digital computer maybe a steam of digital words passed to a digital-to-analog converter (D/A) for conversion to an analog signal. (See analog signal) back to top Dynamic Simulation
The simulation of a dynamic system modeled with integral and differential calculus. This type of modeling is easily accomplished with block-diagram languages such as XANALOG NL-SIM or SIMULINK. back to top Embedded Controller
A digital control computer built into a product that is often hidden from the end user. For example, kitchen appliances, such as a microwave oven, may have a control computer embedded within it. back to top Gimbal
A system of inner and outer rings with pivots arranged for an object, such as a gyro compass, to remain level as the ship moves around. (See Gyroscope) back to top Gyroscope (Gyro)
Gyroscopes are used extensively to sense angular movement and sensor stabilize platforms. Hardware in the loop controlled pitch tables are a common way to test the functionality of gyroscope systems, as well as the connected controller logic. XANALOG’s Model RT-RUG is mainly used in this manner to provided field deployable mission-readiness testing. If the system does not need to be field deployable, XANALOG’s Model RT-300 can be outfitted with the necessary synchro interface. back to top Hardware-in-the-Loop (HIL)
A class of dynamic system simulation where the progression begins with pure simulation designed to mathematically model all the elements of a system. The following phase in the progression is to replace one or more of the mathematical models with the real hardware of the system. (See Real Time) For example, an aerospace engineer using XANALOG hardware-in-the-loop systems typically begins with a complete flight simulation of a missile and use it to debug the flight computer’s software. They then might use the real world interfaces of the XANALOG system to replace the mathematical model of the control surfaces and actuators with the real fin actuators with fins attached. Hardware in the Loop Simulation can be acomplished with either XANALOG’s Model RT-300 system, which runs XANALOG’s NL-SIM Software, or with XANALOG’s Model ReaLINK HIL-3001, which runs SIMULINK models in real-time. back to top Hard Real Time
Through the process of real-time simulation, an upda
te rate is chosen so that the simulations respond with the same rates as the real systems. Within each update of the simulation, the sensors are read, followed by computation of a dynamic model that drives actuators. All steps must be completed within the same chosen update rate. If the rates are not aligned, the computation and real-time input and output will be incomplete and the simulation is able to continue on to the next update.
(See hardware-in-the-loop and real time) back to top Multiplying D/A
Multiplying D/As are used to modulate an analog signal. The analog signal, such as a sine wave, is input to the reference input of the multiplying D/A. It’s amplitude is controlled by a digital number that is applied to the D/A. back to top Pulse-Width Modulation (PWM)
A type of square wave used to control actuators and motors. For example, a square wave varying between 0.0 volts and 10.0 volts within a period of 10 milliseconds. The percent of the time the pulse is at 10.0 volts during each period is the duty cycle of the PWM. back to top Real Time
In the context of the simulation of dynamic systems, real time means the use of simulation designed to respond to a stimulus in the same time frame as it would if the real system was present. (See Hardware-in-the-Loop and Hard Real Time) back to top Resolver
An angle encoding technique using four wires to carry an encoded angle.
(See Synchro) The RT-RUG has the ability to encode and decode either synchro or resolver signals. If the system does not need to be field deployable, XANALOG’s Model RT-300 can be outfitted with the necessary synchro interface. back to top
Synchro
An angle encoding technique using three wires. Typically there are Synchro signal interface boards available for computer systems. These come in two varieties Synchro-signal input or synchro-to-digital
(S/D) and digital-to-synchro (D/S). Synchro encoding is used extensively in pointing-and-aiming applications. (See Resolver)
The RT-RUG has the ability to encode and decode either synchro or resolver signals. If the system does not need to be field deployable, XANALOG’s Model RT-300 can be outfitted with the necessary synchro interface. back to top Thermocouple
A junction of dissimilar metals widely used to measure temperature. back to top | 
