EDNE September 2012 - (Page 58)

AU I TO TIVE MO AERO SP A CE M N G CE Control Systems Digital Control Systems E D S IC S A L MECHATRONICS IN DESIGN Dynamic application of fluid power requires a systems approach. M AT E R IALS PR O Control Electronics RAPHY ROG XE Software mechatronics Mechanical CAD Electromechanics Electronic Systems FRESH IDEAS ON INTEGRATING MECHANICAL SYSTEMS, ELECTRONICS, CONTROL SYSTEMS, AND SOFTWARE IN DESIGN T E Mechanical Systems M S M CO A S CT NSU MER PRODU Fluid power: the hidden giant F By Kevin C Craig, PhD luid-power systems: almost as fast as a speeding bullet, definitely more powerful than a locomotive, and possibly able to leap tall buildings in a single bound. They should sport a Superman logo. This pervasive, hidden technology employs a simple principle that leads people to think that implementation of fluid power is just a select-assemble-and-run task. Nothing could be further from the truth. At the end of the 19th century, in response to the need to more effectively transmit power from one point to another, hydraulic systems replaced traditional mechanical systems. Developers during the Industrial Revolution emphasized fluid power, but most applications were steady in nature and required only static considerations for design. At the beginning of the 20th century, hydraulic-control-system development experienced a major setback, and decades of stagnation followed, with the phenomenal growth of electrical power. The stagnation ended as World War II drove the need for power transmission requiring high effort and fast response, which only hydraulic systems could provide because of their superior power density over electrical devices. Over the next 40 years, industry was the steward of technology for the fluid-power world. A resurgence of interest in fluid-power-control systems is occurring at universities, and industry/university collaboration is growing. Unfortunately, some people consider fluid power a specialist subject. Hydraulic-control systems are essential, however, in applications requiring large forces or torques, with a fast response and high accuracy. They have a better power-to-weight ratio than electrically actuated systems, which are limited by magnetic saturation, and they excel in environmentally difficult applications. In addition, the hydraulic medium is mechanically stiffer than the electromagnetic medium. Self-lubrication and inherent heat transfer are also advantages. Fluid-power applications are numerous. They include vehicle steering, braking, and suspension systems; industrial-mechanical manipulators and robots; and actuators for aircraft and marine vessels. They are all multidisciplinary systems and require a systems approach to design and implement. The required engineering background includes fluid mechanics, electromechanics, system dynamics, computer-control systems, and electronics—in other words, a mechatronics background. Power conversions occur throughout a basic hydrauliccontrol system (Figure 1). A variable-speed-motor-driven pump pressurizes the hydraulic fluid. A relief valve and an accumulator (not shown) regulate and stabilize the pressure of the fluid. A servovalve, driven by an electric valve actuator, provides a controlled supply of fluid into the actuator, which is either a piston-cylinder device or a hydraulic motor, controlling both flow rate and pressure. LowPOWER CONVERSIONS pressure fluid from the servovalve FLUID T, ω (E, I) (Q, P) (T, ω) RESERVOIR is filtered and returned to the resF, V ervoir. A feedback digital-control FLUID RETURN system completes the system. (T, ω) (E, I) HYDRAULIC VARIABLE-SPEED POWER SUPPLY Today, the competitive advanPUMP MOTOR tage of fluid power is greatest in REFERENCE (Q, P) mobile applications, such as mobile INPUT (T, ω) (F, V) heavy equipment, human-assistance HYDRAULIC CONTROLLER VALVE ACTUATOR AND ACTUATOR LOAD SERVOVALVE devices, mobile human-scale equip(LINEAR/ AMPLIFIER (TORQUE MOTOR) ment, and hydraulic hybrid passenROTARY) ger vehicles. In these applications, FEEDBACK fluid power can be a compact, effiSENSOR cient, and effective source of energy transmission. The opportunities are great for mechatronics engineers in Figure 1 Power conversions occur throughout a basic hydraulic-control system. this re-emerging field.EDN www.edn-europe.com 58 EDN EUROPE | SEPTEMBER 2012 U N FA C TU S NS FE DE RI NG E Y S http://www.edn-europe.com

Table of Contents for the Digital Edition of EDNE September 2012

Cover
Contents
International Rectifier
Microchip
RS Components
Masthead
Microchip
EDN Comment
Pulse
Analog Devices
Altera
Baker's best
Messe München
Test & Measurement World
Agilent Techno
Digi-key
Bergquist
Advanced power switches boost microhybrid emissions gains
Digi-Key
Image sensors evolve to address Emerging embedded- vision needs
Renesas
Silicon Labs
Digi-Key
Vicor
Power becomes a software issue as smart phones become smarter
IAN
Power : a significant challenge in EDA design
Digi-Key
Mechatronics in Desin
Design Ideas
Product roundup
Tales from the Cube

EDNE September 2012