In mechanical and control engineering , a servomechanism (also called servo system , or simply servo ) is a control system for the position and its time derivatives , such as velocity , of a mechanical system . It often includes a servomotor , and uses closed-loop control to reduce steady-state error and improve dynamic response. In closed-loop control, error-sensing negative feedback is used to correct the action of the mechanism. In displacement-controlled applications, it usually includes a built-in encoder or other position feedback mechanism to ensure the output is achieving the desired effect. Following a specified motion trajectory is called servoing , where "servo" is used as a verb . The servo prefix originates from the Latin word servus meaning slave.
41-580: ZF AS Tronic is an automated manual transmission made by ZF Friedrichshafen for the motorcoach and lorry market in Europe and North America which was first introduced in 2003. As a part of manual transmission, it lacks the torque converter that is standard on automatic transmissions-an AS Tronic has been quoted as being 500 pounds less than the B500. Some coach operators are choosing this transmission for better fuel economy over automatics. This transmission
82-443: A manumatic , the latter of which is an automatic transmission (automatics use a torque converter instead of a clutch like in an automated manual, to manage the mechanical linkage between the transmission and motor) with the ability to override the automatic transmission's computer, and actuate shifts manually. Add-on AMTs can also function as a regular manual gearbox (with a manual shift lever), whereas integrated AMTs do not need
123-422: A "normal" shift layout, so they can be designed with an optimized AMT shifting layout (which would have an unusual pattern to manually shift). Integrated AMTs either have gear-selector drums (which allows only serial shifting and no gear-skipping, but this system is fairly inexpensive, because it needs only one actuator), or single actuators. Single-actuator systems require one actuator for each shifting sleeve (which
164-429: A conventional automatic transmission ), while traditional semi-automatic and clutchless manuals require the driver to manually select the gear even when the engine is at redline, since they automate only part of the transmission (namely the clutch), and will not shift gears by themselves. Despite the superficial similarity, automated manual transmissions differ significantly in internal operation and driver's "feel" from
205-416: A given motor power). Potentiometers are subject to drift when the temperature changes whereas encoders are more stable and accurate. Servomotors are used for both high-end and low-end applications. On the high end are precision industrial components that use a rotary encoder. On the low end are inexpensive radio control servos (RC servos) used in radio-controlled models which use a free-running motor and
246-427: A microcontroller) sends pulse-width modulation (PWM) signals to the servo. The electronics inside the servo translate the width of the pulse into a position. When the servo is commanded to rotate, the motor is powered until the potentiometer reaches the value corresponding to the commanded position. James Watt 's steam engine governor is generally considered the first powered feedback system. The windmill fantail
287-828: A rotary (angular) or linear output. Speed control via a governor is another type of servomechanism. The steam engine uses mechanical governors; another early application was to govern the speed of water wheels . Prior to World War II the constant speed propeller was developed to control engine speed for maneuvering aircraft. Fuel controls for gas turbine engines employ either hydromechanical or electronic governing. Positioning servomechanisms were first used in military fire-control and marine navigation equipment. Today servomechanisms are used in automatic machine tools , satellite-tracking antennas, remote control airplanes, automatic navigation systems on boats and planes, and antiaircraft -gun control systems. Other examples are fly-by-wire systems in aircraft which use servos to actuate
328-424: A sequential mode, where the driver can upshift or downshift by only one gear at a time. However, this is not the case for all modern transmissions. For example, BMW's "SMG" and Ferrari's "F1" transmission can skip gears on both downshifts and upshifts, when selecting gears manually via the steering wheel-mounted paddle-shifters, as seen on most modern transmissions. Older clutchless manual transmissions (mostly prior to
369-455: A simple potentiometer position sensor with an embedded controller. The term servomotor generally refers to a high-end industrial component while the term servo is most often used to describe the inexpensive devices that employ a potentiometer. Stepper motors are not considered to be servomotors, although they too are used to construct larger servomechanisms. Stepper motors have inherent angular positioning, owing to their construction, and this
410-519: Is an earlier example of automatic control, but since it does not have an amplifier or gain , it is not usually considered a servomechanism. The first feedback position control device was the ship steering engine , used to position the rudder of large ships based on the position of the ship's wheel. John McFarlane Gray was a pioneer. His patented design was used on the SS Great Eastern in 1866. Joseph Farcot may deserve equal credit for
451-410: Is combined with a rotary encoder or a potentiometer to form a servomechanism. This assembly may in turn form part of another servomechanism. A potentiometer provides a simple analog signal to indicate position, while an encoder provides position and usually speed feedback, which by the use of a PID controller allow more precise control of position and thus faster achievement of a stable position (for
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#1732775654595492-454: Is generally used in an open-loop manner without feedback. They are generally used for medium-precision applications. RC servos are used to provide actuation for various mechanical systems such as the steering of a car, the control surfaces on a plane, or the rudder of a boat. Due to their affordability, reliability, and simplicity of control by microprocessors, they are often used in small-scale robotics applications. A standard RC receiver (or
533-399: Is not a servomechanism, as there is no automatic feedback that controls position—the operator does this by observation. By contrast a car's cruise control uses closed-loop feedback, which classifies it as a servomechanism. A common type of servo provides position control . Commonly, servos are electric , hydraulic , or pneumatic . They operate on the principle of negative feedback, where
574-720: Is notably favored over conventional automatic and CVT transmissions due to its lower cost. Automated manual transmissions can be semi-automatic or fully-automatic in operation. Several different systems to automate the clutch and/or shifting have been used over the years, but they will generally use one of the following methods of actuation for the clutch and/or shifting: hydraulic or electro-hydraulic actuation , electro-mechanical , pneumatic , electromagnetic , or even purely electrical using an electric motor . Gear shifting, clutch actuation, shift-timing, and rev-matching are all under automated control via electronic sensors, computers, and actuators. When shifting gears,
615-513: Is offered as 6-speed (called AS Tronic Lite by ZF), 10-speed 12-speed or 16-speed transmission. Automated manual transmission The automated manual transmission ( AMT ) is a type of transmission for motor vehicles . It is essentially a conventional manual transmission equipped with automatic actuation to operate the clutch and/or shift gears . Many early versions of these transmissions that are semi-automatic in operation, such as Autostick , which automatically control only
656-491: Is the 1955 Citroën DS , which used a 4-speed "BVH" transmission. This semi-automatic transmission used an automated clutch, which was actuated using hydraulics . Gear selection also used hydraulics, however, the gear ratio needs to be manually selected by the driver. The 1956 Renault Dauphine 3-speed manual transmission was available with an optional Ferlec automated clutch, which used an electromagnetically-operated clutch system. Other clutchless manual transmissions included
697-526: Is why this type of system is more expensive, but it also shifts faster). The actuators can either be electro-hydraulic (more expensive, but faster, well-suited for single-actuator systems, and allow for higher torque), or electro-mechanical (less expensive, but usually limited to 250 N·m (184.5 lb-ft ) of gearbox input torque). This limit is because the clutch actuation force increases with higher torque, and short shifting times; electro-mechanical actuators are just electric motors – using larger motors reduces
738-570: The E36 M3 coupe. Although the name "SMG" was an abbreviation of "Sequential Manual Gearbox", the transmission internal were as per a typical (synchromesh-equipped) manual transmission, not a true sequential manual transmission . The SMG was replaced by the SMG-II when the E46 M3 was introduced in 2000. BMW's final AMT (before being replaced by a dual-clutch transmission) was the 7-speed SMG-III used in
779-470: The clutch – often using various forms of clutch actuation , such as electro-mechanical , hydraulic , pneumatic , or vacuum actuation – but still require the driver's manual input and full control to initiate gear changes by hand. These systems that require manual shifting are also referred to as clutchless manual systems. Modern versions of these systems that are fully automatic in operation, such as Selespeed and Easytronic , can control both
820-593: The "Shift-tronic" 6-speed semi-automatic was offered on the Alpina B12 coupe (based on the E31 850CSi). Using an automated clutch paired to a standard H-pattern shifter (as per the Ferrari Mondial T), the transmission was supplied by LuK and fitted to less than 40 cars. Mass-production of automated manual transmissions began for BMW in 1997 with the introduction of the "SMG" 6-speed automatic transmission in
861-667: The 1940s and 1950s. An early example of this transmission was introduced with the Hudson Commodore in 1942, called Drive-Master . This unit was an early semi-automatic transmission , based on the design of a conventional manual transmission which used a servo-controlled vacuum-operated clutch system, with three different gear shifting modes, at the touch of a button; manual shifting and manual clutch operation (fully-manual), manual shifting with automated clutch operation (semi-automatic), and automatic shifting with automatic clutch operation (fully-automatic). Another early example
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#1732775654595902-452: The 1967 NSU Ro 80 (3-speed Fichtel & Sachs ) and 1967 Porsche 911 (4-speed Sportomatic ), both of which used vacuum-actuated clutches and hydraulic torque converters. The 1968 Volkswagen Beetle and Volkswagen Karmann Ghia offered a 3-speed Autostick transmission, which used an electric switch on the gear shifter connected to a solenoid , to operate the electro-pneumatic vacuum clutch servo . In 1963, Renault switched from
943-522: The 1990s) will retain H-pattern shifters, plus the shift gate, and will require the driver to select the required gear ratios manually. The clutch, however, will be a servo-controlled unit , connected to various actuators , a solenoid and sensors which control the clutch automatically. Another alternate means of clutch automation is the "clutch-by-wire" system. The system generally uses an electric actuator and electronic sensors , which replace
984-440: The 2004-2010 BMW E60 M5 and related BMW E63 M6 . The SMG-III could achieve a shift time of 65 milliseconds in its most aggressive mode From 2002 to 2007, the third-generation Toyota MR2 was available with an "SMT" 6-speed automated manual transmission. The SMT system utilized an electro-hydraulic activation system for both the clutch and shifting, but no H-pattern shifter like with the standard transmission. Instead, there
1025-669: The Ferrari 458 in 2009. Sister company Alfa Romeo introduced the related Selespeed 5-speed automatic transmission for the Alfa Romeo 156 in 1999. This was followed by Maserati's 2001 introduction of the related Cambiocorsa 6-speed automatic transmission in the Maserati Coupé . Selespeed was also used in the Fiat Punto and Stilo models. BMW 's involvement with automated manual transmissions began in 1993, when
1066-472: The Japanese domestic market only). This transmission, originally designed for trucks, was based on a manual transmission with the addition of hydraulic actuators for the gear shifter and the clutch. Initial versions did not allow direct selection of gear ratios, instead allowing drivers only to lock out higher gears (as per many traditional automatic transmissions). Later versions added a manual mode, allowing
1107-413: The aircraft's control surfaces, and radio-controlled models which use RC servos for the same purpose. Many autofocus cameras also use a servomechanism to accurately move the lens. A hard disk drive has a magnetic servo system with sub-micrometer positioning accuracy. In industrial machines, servos are used to perform complex motion, in many applications. A servomotor is a specific type of motor that
1148-444: The automated clutch to a fully-automatic 3-speed Jager transmission, which consisted of an electro-mechanical control unit that operated both the clutch and shifting, effectively making it one of the earliest automated manual transmissions. The Jager transmission was controlled via dash-mounted electronic push-buttons. The Isuzu NAVi5 5-speed automatic transmission was introduced in the 1984 Isuzu Aska mid-size sedan (sold in
1189-605: The clutch operation and the gear shifts automatically, by means of an ECU , therefore requiring no manual intervention or driver input for gear changes. The usage of modern computer-controlled AMTs in passenger cars increased during the mid-1990s, as a more sporting alternative to the traditional hydraulic automatic transmission. During the 2010s, AMTs were largely replaced by the increasingly widespread dual-clutch transmission , but remained popular for smaller cars in Europe and some developing markets , particularly India , where it
1230-475: The clutch, while the gearshift mechanism was a standard H-pattern shifter operated as per normal transmissions. In 1997, the Ferrari F355 became available with an "F1" 6-speed transmission, which uses paddle-shifters located behind the steering wheel or can be driven in a fully-automatic mode. The F355's successors offered similar transmissions, until the company switched to a dual-clutch transmission for
1271-416: The control input is compared to the actual position of the mechanical system as measured by some type of transducer at the output. Any difference between the actual and wanted values (an "error signal") is amplified (and converted) and used to drive the system in the direction necessary to reduce or eliminate the error. This procedure is one widely used application of control theory . Typical servos can give
ZF AS Tronic - Misplaced Pages Continue
1312-437: The driver selects the desired gear with the transmission shift lever , while electronic sensors and actuators connected to a TCU (transmission computer) or microprocessor will automatically operate the clutch and throttle to match revs and to re-engage the clutch in milliseconds. Torque and power transfer to the drive wheels will also be electronically controlled. Most modern implementations of this transmission function are in
1353-586: The driver to control the gear selection. Several companies owned by Fiat S.p.A. were influential in the development of automated manual transmissions. Ferrari 's involvement with automated manual transmission began with the 7-speed semi-automatic paddle-shift transmission used in the 1989 Ferrari 640 Formula One racing car. In 1992, the Ferrari Mondial T introduced the option of a "Valeo" 5-speed semi-automatic transmission. This transmission used an electro-mechanical actuator to automatically operate
1394-469: The error towards zero. The Ragonnet power reverse mechanism was a general purpose air or steam-powered servo amplifier for linear motion patented in 1909. Electrical servomechanisms were used as early as 1888 in Elisha Gray 's Telautograph . Electrical servomechanisms require a power amplifier. World War II saw the development of electrical fire-control servomechanisms, using an amplidyne as
1435-422: The feedback concept, with several patents between 1862 and 1868. The telemotor was invented around 1872 by Andrew Betts Brown , allowing elaborate mechanisms between the control room and the engine to be greatly simplified. Steam steering engines had the characteristics of a modern servomechanism: an input, an output, an error signal, and a means for amplifying the error signal used for negative feedback to drive
1476-399: The mechanical clutch linkage or hydraulic clutch connection, to monitor and control clutch positioning, completely replacing the hydraulic linkage between the mechanical clutch and pedal itself with a single electro-mechanical actuator. Depending on the mechanical build and design, some (mostly modern) automated manual transmissions will automatically shift gears at appropriate points (like
1517-771: The motor dynamics due to the motors' higher mass moment of inertia (which is not good for fast shifting), and bigger motors also put more stress on the car's 12-volt electrical system. As a result, one can have either slow shifting and a very large lead-acid battery (not suitable for cars), or fast shifting and a smaller battery (works up to 250 N·m of torque). Modern AMTs, such as Suzuki Auto Gear Shift and Dacia/Renault Easy-R , usually operate in conjunction with electronic throttle control to initiate gear shifts based on certain RPM and/or throttle position. The automated manual transmission has its origins in early clutchless manual transmissions that began to appear on mass-production cars in
1558-613: The power amplifier. Vacuum tube amplifiers were used in the UNISERVO tape drive for the UNIVAC I computer. The Royal Navy began experimenting with Remote Power Control ( RPC ) on HMS Champion in 1928 and began using RPC to control searchlights in the early 1930s. During WW2 RPC was used to control gun mounts and gun directors. Modern servomechanisms use solid state power amplifiers, usually built from MOSFET or thyristor devices. Small servos may use power transistors . The origin of
1599-542: The word is believed to come from the French " Le Servomoteur " or the slavemotor, first used by J. J. L. Farcot in 1868 to describe hydraulic and steam engines for use in ship steering. The simplest kind of servos use bang–bang control . More complex control systems use proportional control, PID control , and state space control, which are studied in modern control theory . Servos can be classified by means of their feedback control systems: The servo bandwidth indicates
1640-520: Was a shift lever that could be pulled and pushed forward or backward to upshift and downshift, as well as the addition of electronic steering-wheel-mounted shift buttons. Brands within the Volkswagen Group have typically used dual-clutch transmissions instead of automated manual transmissions, however a 6-speed "E-gear" automated manual transmission was introduced for the 2004 Lamborghini Murciélago . and Lamborghini Gallardo . The E-gear
1681-479: Was used on the successors to the Murciélago and Gallardo, and it was also available on the 2007-2012 Audi R8 (Type 42) , marketed as the "R-tronic" transmission. Servomechanism The term correctly applies only to systems where the feedback or error-correction signals help control mechanical position, speed, attitude or any other measurable variables. For example, an automotive power window control