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the attempt to satisy some need of a living organism. In the lower organisms, a drive is expressed in instinctive reactions; in higher animals, a drive is mediated by acquired individual experience. A drive has an inherent direction that can manifest itself either in a vague striving toward something or in seeking a definite object. Drive represents an important aspect of the living organism’s behavior; it acts as an internal stimulus for the accomplishment of a definite action. It affects the entire range of sensory and motor manifestations of the living creature, altering the tension in the body, organizing its attitudes, and so on. A drive is characterized by constancy of appearance and periodicity of its course; the satisfaction of a drive is accompanied by a reduction of tension in the organism.
Originating independently of the consciousness (thought and volition) of a person, a drive is connected to the sphere of activating motives and interests of an individual that determine the form and direction of the realization of the drive: drives can be inhibited or repressed, transferred from one object to another, and so on. Different drives can enter into a conflict that is resolved in the process of the struggle between motives. The diversity of forms in which human drives appear makes their formal systematization difficult. In psychology, attempts have been made to reduce the entire diversity of emotional life to one or two basic drives (for example, the drive of a sexual nature—libido—and the death instinct of S. Freud, A. Adler’s drive to power) as well as to construct an extensive classification of drives proceeding from a recognition of the multitude of various strivings (for example, 18 in W. McDougall’s system). Drives are a subject of special study in psychoanalysis and in other schools of dynamic psychology (McDougall, K. Lewin, and others).
in mechanical engineering, a mechanism for the transmission of continuous rotary motion. Drives are used in various kinds of transmissions to increase or decrease speed, to regulate speed in a continuous or discontinuous manner, to change the direction of motion, and to actuate several mechanisms by means of one motor. The principal characteristics of a drive are transmitted moment, angular velocity, gear ratio, and efficiency.
Two basic types of drives are distinguished: mechanical— including rigid-component, hydraulic, and pneumatic drives— and electric. Important varieties of mechanical drives are those based on the use of gears—such as gear drives, chain drives, and worm gears—and traction drives—for example, belt drives and friction drives. Such varieties are widely used in mechanisms with fixed gear ratios as well as in low- and medium-power mechanisms with variable gear ratios; they are used, for example, in gear boxes and as variable-speed drives in machines, motor vehicles, and tractors. Hydraulic and electric drives that permit the transmission of greater power and have a simple and convenient automatic control system are used in various areas of machine building, especially in heavy transport vehicles.
I. G. GERTSKIS
a power plant that sets a machine or mechanism in motion. Drives usually consist of a power source, a connecting mechanism, and control apparatus. The power source may be a heat, electric, pneumatic, hydraulic, or other type of engine or a device that releases stored mechanical energy, such as a spring, inertial, or weight mechanism. In some cases muscle power provides the drive—for example, in hand-operated winches and in some calculating and household mechanisms and machines, such as adding machines, sewing machines, and bicycles.
A distinction is made among group, individual, and multi-motor drives, according to the type of power distribution. In a group drive, motion is transmitted from a single motor to a group of operating machines or mechanisms through one or more transmissions. Because of technical deficiencies, group drive has been almost entirely supplanted by individual drive, in which each operating machine has its own motor and transmission. This makes possible operation with a more suitable speed of rotation, as well as reversing and rapid starting and slowing of machines. In a multimotor drive, the separate operating members of a machine are driven by their own motors and transmission systems. Such a drive makes possible machines of compact design and the use of automatic control. Multimotor drive is used in complicated machine tools, rolling mills, and hoisting and transport machines.
A distinction according to purpose is made among stationary drives, which are rigidly mounted on a bedplate or foundation; mobile drives, which are used in moving power tools; and transport drives, which are used for a variety of vehicles. The most common stationary type is the electric drive, in which an electric motor is the source of mechanical power; in moving power tools and vehicles, heat engines with direct mechanical or electric transmissions are most often used. Hydraulic machine drive and pneumatic drives, in which the energy of compressed air produced by a compressor is converted into mechanical power by compressed-air motors, are also used in industry.
The development of the various drive systems is associated with the construction and improvement of motors. Even the first steam engines, such as those of J. Watt and I. I. Polzunov, required the use of connecting and control mechanisms that, in combination with the steam engine, made possible an economical, continuously operating source of mechanical power that did not depend on natural conditions. With the subsequent development of drives, steam and hydraulic turbines and internal-combustion engines were built. Since the turn of the 20th century these engines, in combination with mechanical transmissions, became the most important type of drive for motor vehicles, aircraft, tractors, and excavators.
In the early 20th century the use of electric motors in the drives of industrial machines gained wide acceptance: DC types were used at first, followed by three-phase induction motors, which are very efficient, reliable, and economical. The shift to the use of individual and multimotor drives in machines, particularly lathes and forging and pressing machines, made possible the arrangement of machines in the required sequence and laid the foundations for the development of mass production. The combination of the electric drive with the machine tool made possible the creation of automatic machine tools and then of automatic systems of machines and a changeover to production control using computers. The electric drive also became widely used in household appliances, such as sewing machines, washing machines, kitchen appliances, and electric shavers.
The major role in drives for transportation machines has been retained by internal-combustion engines (in motor vehicles, diesel locomotives, and motor ships), gas turbines (in aircraft and gas-turbine locomotives), and nuclear power plants (in submarines, icebreakers, and warships). By the early 1970’s about 80 percent of the power of existing engines was in the transportation sector. Composite drives, such as steam turbines with heat engines or gas turbines, hydraulic drives with electric motors, and so on (hydraulic-electric drive, gas-turbine-hydraulic drive), are used to provide for performance under complex operating conditions.
The capacity of a drive depends on the power of the motor used. The power for the drives of modern machines ranges from tens of megawatts for screw propellers, powerful pumps, and the blowers in wind tunnels to fractions of a watt for miniature drives in electric clocks.
The use of transmission mechanisms in machine drives results from a number of design and service factors: (1) because of layout conditions, overall dimensions, and safety considerations, the motor cannot always be connected directly to the operating mechanism; (2) the speeds required for the machine do not usually match the optimum speed of rotation of the motor; (3) in most industrial and transport machines, provision must be made for speed regulation and for operation at low speeds with high torque (regulation of the motor speed is not always possible or economical); (4) motors are designed mainly for uniform rotational motion, but the operating members of machines often perform translatory, helical, and other types of motion, as well as motion according to a prescribed program of speed variations.
The transmissions in machine drives are made with a constant or adjustable gear ratio. The most commonly used types include mechanisms that maintain a constant gear ratio, such as reduction gears and multipliers (which reduce and increase the rate of rotation, respectively); gearboxes, which permit stepwise variation of the rate of rotation; variable-speed drives, which provide stepless adjustment of the number of revolutions and optimum speed conditions; and various open transmissions, such as belt, chain, and gear drives. Remote-control and monitoring mechanisms in automobiles, tractors, and motorcycles are driven by means of flexible shafts.
In addition to mechanical transmissions, electric and hydraulic types are also used in machine drives. There are also “built-in” drives, which are mounted entirely within an operating unit of a machine—for example, the electrically driven drums of belt conveyors and hoists, the drive rollers of roller conveyors, and the motor wheels of heavy-duty trucks.
The control apparatus of a drive is used for starting, stopping, slowing, and changing the direction of rotation; adjusting the speed; protecting motors and mechanisms of machines from overloads and damage; and providing interlocks for the individual mechanisms.
Drive control systems may be manual, semiautomatic, or automatic. In a manual system all the control operations are performed by apparatus that acts on the power circuit of the motor (knife switches, controllers, rheostats, and so on) or on its power-supply or ignition system. With semiautomatic control, special signaling devices, such as knobs, pedals, master controllers, and position and limit switches, are operated directly. The contacts of the signaling devices are connected to the low-power auxiliary circuits of relays and contactors, which in turn switch the power circuits of the motors without direct human intervention. With automatic control, an initial pulse for starting the drive is transmitted from mechanical or electrical relays or from other apparatus, such as sensors. The subsequent automatic operation of the system is maintained and monitored by electric, mechanical, hydraulic, or other apparatus, such as regulators, selectors, photoelectric and thermoelectric cells, or logic, programming, or television devices.
Automatic control of a drive permits speed adjustment according to a preset program as a function of the route, time, or load. It also makes possible regulation of acceleration and deceleration, redistribution of loads among the drives, accurate stopping or reversing of all or individual drives, and protection from overloads, overspeeding, or improper initial position. The use of automation—even partial automation—improves the reliability and accuracy of the drive’s operation, increases the overall productivity of machines, and makes remote control possible. In a number of cases the automation of a drive is dictated by industrial safety requirements, such as the undesirability of placing workers in a toxic or dusty environment or of working with radioactive materials. Automation of drive control also makes possible a transition from individual control of machine operations to the automatic control of production units, areas, and shops.
A. A. PARKHOMENKO
What does it mean when you dream about driving?
The sense of guiding, of being in control, of being at the helm. Vehicles such as cars often represent the physical body, so what happens to us in driving dreams can indicate something about the body. “Drive” is also a component of many idioms, from “driving a hard bargain” to “driving someone over the edge.”
drive(1) An electromechanical device that contains and reads and writes magnetic disks, optical discs or magnetic tapes. See magnetic disk, optical disc and magnetic tape.
(2) A solid state flash drive that contains no moving parts. See USB drive.
(3) To provide power and signals to a device. For example, "this control unit can drive up to 15 terminals."