Showing papers on "Drive wheel published in 2020"

Considerations for Determining the Coefficient of Inertia Masses for a Tracked Vehicle

Abstract: The purpose of the article is to present a point of view on determining the mass moment of inertia coefficient of a tracked vehicle. This coefficient is very useful to be able to estimate the performance of a tracked vehicle, including slips in the converter. Determining vehicle acceleration plays an important role in assessing vehicle mobility. Additionally, during the transition from the Hydroconverter to the hydro-clutch regime, these estimations become quite difficult due to the complexity of the propulsion aggregate (engine and hydrodynamic transmission) and rolling equipment. The algorithm for determining performance is focused on estimating acceleration performance. To validate the proposed model, tests were performed to determine the equivalent reduced moments of inertia at the drive wheel (gravitational method) and the main components (three-wire pendulum method). The dynamic performances determined during the starting process are necessary for the validation of the general model for simulating the longitudinal dynamics of the vehicle. Finally, the differential and algebraic equations of the virtual model approximate more accurately the actual process of the operation of the vehicle. The virtual model, through the data obtained from the simulation process, allows for the determination, indirectly, of the variation of the mass moment of inertia coefficient and its expression of approximation.

Bundled Rotary Helix Drive Mechanism Capable of Smooth Peristaltic Movement

Abstract: Herein, we focus on the design method of a robot, named Wave Wheel, capable of generating a smooth continuous peristaltic wave, which is driven by a bundled rotary helix drive mechanism. Wave Wheel mainly consists of a braided mesh tube, multiple helices that are arranged on the circumference, and spur gears. When a single motor rotates the helices, the wheel generates peristaltic waves. The proposed mechanism has some unique characteristics: (i) In principle, smooth peristalsis can be generated with a simple structure. (ii) It can be driven by a single motor and can propagate waves at high speed by infinite rotation of the shaft. (iii) The structure is a circle in the transversal plane and can be used as an omnidirectional drive wheel. The basic design method, such as waveform, velocity, and the collision condition are discussed from a geometrical point of view. Based on the model accounting for the mechanical constraints, we have designed and fabricate a prototype robot and experimentally tested it. The prototype (diameter of 57 mm) reached the top speed of the peristaltic locomotion of 43 mm/s when angular velocity of the helix was 60 rad/s. We obtained the trajectory of the mesh surface by motion capture, and the result showed that the velocity was not constant on the whole surface but periodically changed with time due to the sliding between the mesh and the helix.

Increase of operating reliability of the travel wheel using the use of the elastic inserts

Abstract: The aim of research is to substantiate the rational design of the travel wheel based on the determination of the dynamic forces arising from the movement of the freight carriage and the crane bridge. The research methodology is based on analytical methods for studying dynamic forces in the mechanism of movement of the cargo carriage of an overhead crane. The obtained solution of the three-mass dynamic scheme of the movement of the freight carriage. To verify the theoretical data obtained, an experiment was carried out on an overhead crane with a lifting capacity of 5 , span of 22.5 m, lifting height of 8 m, operating mode of 7 K. The study of the vibration state was carried out on the crane beam in the middle of the span, on the axis of the driven wheel of the crane trolley with an elastic insert and on the axis of the drive wheel of the crane trolley of a conventional design. Crane wheels are the fastest wearing parts of a crane. A decrease in their durability leads to an increase in repair costs and crane downtime. Therefore, increasing the durability of crane travel wheels is an urgent task of modern crane construction. All designs of travel wheels are quite rigid and do not perceive shocks and distortions arising from the deviation of the rail track from the recommended values and lead to significant wear of the flanges and rails. The analysis of the obtained solutions showed that when using a travel wheel with an elastic insert, the dynamic factors during the movement of the freight carriage decrease. Dependences are obtained for determining the dynamic forces arising from the movement of the travel crane wheel, taking into account the rigidity of the elastic ring, which is installed in the travel wheel. The analysis of the regularities of the formation of vibration signs at different points of the overhead crane structure is carried out. The proposed design and calculation method for a travel wheel with an elastic insert improves its operational reliability

Method and apparatus for power transfer to an independent moving cart during travel along a track

Abstract: A system and method for providing power to independent movers traveling along a track in a motion control system without requiring a fixed connection between the mover and a power source external to the mover. In one embodiment, a sliding transformer transfers power between the track and each mover. In another embodiment, an optical transmitter transfers power between the track and an optical receiver mounted on each mover. In yet another embodiment, a generator includes a drive wheel engaging the track as each mover travels along the track. A power converter on the mover receives the power generated on and/or transmitted to the mover to control an actuator or a sensor mounted on the mover or to activate drive coils mounted on the mover to interact with magnets mounted along the track and, thereby, control motion of each mover.

A salt push plate pulling device

Abstract: The present invention relates to a salt pusher traction device used for salt collection in a salt farm. The present invention is formed to move back and forth by the signal of a wireless remote controller and wind and unwind a rope connected to a pusher of a salt farm by comprising: a drive wheel frame in which a plurality of pulley type drive wheel shafts coupled to a drive wheel shaft are installed at the bottom of the frame to roll over rails installed on a bank, and rail support plates are coupled to the upper side of both rails; a drive motor which is installed in a central part of a drive motor support bar whose cross section is coupled in a V shape between the both rail support plates, and drives the drive shaft of the drive wheels by a power transmission means; a plurality of lower rollers which are installed in a lower roller shaft fixated to face the outside of four corners of the drive wheel frame; a rotating ring which is placed on the upper part of the lower rollers to rotate; a rotating ring support bar which is fixated to the outside of the rotating ring; a power control unit support which is fixated on one side of the rotating ring support bar; a battery and a control box which are installed on the upper part of the power control unit support; a wire connection pipe which protrudes from the power control unit support to the center of the rotating ring; a rope reel support which is fixated on the other side of the rotating ring support bar; a rope reel motor and a rope reel which are installed on the rope reel support; and a control unit which controls the drive motor and the rope reel motor by being installed in the control box and has a wireless reception unit receiving the signal of the wireless remote controller. The present invention is able to protect the floor of a salt farm and reduce required manpower.

Omni-directional grinder for door handle

Abstract: The invention discloses an omni-directional grinder for a door handle. Through cooperative arrangement of a servo motor A, a lead screw A and a lifting plate provided with a nut A, a fixed frame can ascend and descend through the lifting plate. Through cooperative arrangement of a drive motor, a driving wheel, a drive wheel and an abrasive belt, the rotating abrasive belt can grind the to-be-ground door handle. Through cooperative arrangement of a servo motor B, a lead screw B, a sliding plate, linear guide rails A, a servo motor C, a lead screw C, a sliding seat, a linear guide rail B, a servo motor B, a rotating seat, a servo motor E and a door handle mounting plate, the door handle can have multiple moving and rotating freedom degrees, and the door handle can be converted to the designated front-and-back position or left-and-right position or rotating angle so as to be attached to the abrasive belt to achieve grinding. According to the omni-directional grinder, omni-directional grinding can be carried out on the door handle, the ground door handle can keep good quality, production efficiency is high, the burdens of machining personnel are relieved, and use is safe and convenient.

Single drum surface compactor machine

Abstract: A surface compactor machine includes a cylindrical drum defining a cylindrical space in an interior portion of the cylindrical drum and having a central axis of rotation, and a counterweight in the cylindrical space. The compactor further includes a non-driven support wheel affixed to the counterweight and in contact with an underlying portion of an interior surface of the cylindrical drum beneath the counterweight. A drive motor is provided in the cylindrical space, and a drive wheel is mechanically rotatable by the drive motor. The drive wheel contacts an inner surface of the cylindrical drum such that rotation of the drive wheel by the drive motor urges the cylindrical drum to rotate about the central axis of rotation.

Estimation of Transmission Input&Output Shaft Torque and Drive Wheel Speed for Compound Power Split Powertrain Based on Unknown Input Observer

Abstract: Precise estimation of transmission input&output shaft torque and wheel speed is significant to the development of torque distribution and coordinated control method for the power split hybrid powertrain system. This paper studies an estimation method of transmission input and output torque as well as drive wheel speed using an unknown input observer in different operating modes for a compound power split hybrid powertrain system. Firstly, the configuration and dynamic characteristic of power split transmission is analyzed. Then, state equations in different operating modes are established, and a Takagi-Sugeno (T-S) fuzzy model is utilized to deal with the nonlinearities of load resistance torque. Furthermore, an unknown input reduced-order observer is designed to estimate the transmission input&output shaft torque and wheel speed. The asymptotical stability of the developed observer is verified based on Lyapunov theory. Finally, the performance of the unknown input observer is assessed by comparing with the Luenberger observer based on Matlab/Simulink simulation platform and test bench. Simulation and experiment results show that, the proposed observer can estimate the transmission input&output shaft torque and wheel speed more effectively in different operating modes.

Internal combustion engine control device

Abstract: To provide an internal combustion engine control device in which an accelerator operation member is operated to an opening direction in a state that an internal combustion engine mounted to an automatic two-wheel vehicle is operated, and which can suppress an excessive large roll motion of the automatic two-wheel vehicle which is generated when increasing an angular speed of a crankshaft of the internal combustion engineSOLUTION: In an internal combustion engine control device 11, a state of the transmission of a drive force to a drive wheel from a crankshaft includes a block state for blocking the transmission of the drive force, and a transmission state for transmitting the drive force A control part 12 performs suppression processing for suppressing the drive force so as to be capable of acquiring an operation amount of the accelerator operation member of the automatic two-wheel vehicle, and so that a magnitude of the drive force in the block state becomes smaller than the magnitude of the drive force in the transmission state with respect to an increase amount of the operation amount having the same magnitudeSELECTED DRAWING: Figure 2

Controller and control method

Abstract: The present invention obtains a controller and a control method capable of securing a driver's comfort during adaptive cruise control for a straddle-type vehicle.In the controller and the control method according to the present invention, during the adaptive cruise control in which the straddle-type vehicle is made to travel according to a distance from the straddle-type vehicle to a preceding vehicle, motion of the straddle-type vehicle, and a driver's instruction, when a state where a braking force is generated on at least one of wheels of the straddle-type vehicle is switched to a state where a drive wheel is driven using drive power output from a drive source of the straddle-type vehicle, the braking force generated on the at least one of the wheels is controlled such that a reference braking force is generated on the drive wheel at a time point at which the drive wheel starts being driven due to transmission of the drive power output from the drive source to the drive wheel.

Driving force control device for vehicle

Abstract: The invention provides a driving force control device for a vehicle, which can suppress rapid change of driving torque and braking torque and eliminate slipping when slipping occurs. A drive force control device for a vehicle is provided with: a differential mechanism that divides and transmits torque from a torque generation mechanism to a right drive wheel and a left drive wheel, and differentially couples the right drive wheel and the left drive wheel; and a differential restriction mechanism that restricts the differential motion between the right drive wheel and the left drive wheel, andwhen the slip ratio of the one of the right drive wheel and the left drive wheel with the smaller slip ratio is greater than an allowable value, executes: differential restriction control that restricts the differential rotational speed between the right drive wheel and the left drive wheel to be within a predetermined value by the differential restriction mechanism; and slip control for limitingthe torque of one of the right drive wheel and the left drive wheel having a smaller slip ratio (step S18).

Track assembly and carriage assembly for a vehicle

Abstract: A vehicle includes a carriage assembly and a track assembly. The carriage assembly includes a central roller flanked by side rollers on an axle. A carriage rail can support the axle. The track assembly includes a rack screw positioned in a lower portion of a channel. The channel receives the carriage assembly such that a drive wheel can engage with the rack screw.

Integrated park brake system for a riding lawn care vehicle

Abstract: A riding lawn care vehicle may include a frame, a steering assembly, a first brake assembly, and a first biasing assembly. A first drive wheel and a second drive wheel of the riding lawn care vehicle are operably coupled to the frame. The steering assembly includes a first steering lever and a second steering lever. The first and second steering levers are operably coupled to corresponding ones of the first and second drive wheels via a first hydraulic motor and a second hydraulic motor, respectively, to facilitate turning of the riding lawn care vehicle based on drive speed control of the first and second drive wheels responsive to positioning of the first and second steering levers to control the first and second hydraulic motors. The first brake assembly is operably coupled to the first hydraulic motor to enable a braking force to be selectively applied to a motor shaft of the first hydraulic motor responsive to movement of the first steering lever from an inboard position to an outboard position. The first biasing assembly is configured to positively assist movement of the first steering lever between the inboard and outboard positions in both directions.

Rear fender assemblies for a work vehicle

Abstract: A track work vehicle includes a track system including a drive wheel supported by an axle housing that drives a continuous ground-engaging track, a saddle assembly that guides the track about the drive wheel and an undercarriage frame that supports one or more idler wheels that guide the track along a ground surface. The track work vehicle further includes a fender assembly that includes at least one fender coupled to the axle housing to overlap a portion of the track.

Braking device for movable-type belt conveyor

Abstract: The invention discloses a braking device for a movable-type belt conveyor. The braking device includes a frame, two transmission rollers rotatably connected to the two ends of the frame and a conveyorbelt arranged on the transmission rollers in a winding mode, an internal bolt of the frame is fixedly connected with a drive motor and an electric hoist, a central shaft is rotatably connected to theinner side of the frame, and a first drive wheel, a braking mechanism and a second drive wheel sleeve the central shaft. According to the braking device, when a foot switch is stepped, the electric hoist is switched on, so that the electric hoist acts, when the foot switch is released, the electric hoist rotates, an output shaft of the electric hoist carries out receiving and winding connection on a connected elastic sheet so as to enable the inner side of the elastic sheet to be close to the central shaft, when deceleration blocks on the elastic sheet are in contact with the central shaft, the central shaft is braked, and the conveyor belt is indirectly braked, when the degree of winding connection of the electric hoist increases, the number of the deceleration blocks in contact with thecentral shaft is increased, so that the frictional force on the central shaft is increased, and the braking effect is increased.

Sweep auger drive shield with gravity reclaim

Abstract: A sweep auger system having a driveshaft with auger flighting and a backboard extending a length from an inward end to an outward end. An input of a gearbox is connected to an outward end of the drive shaft and a sweep wheel having a plurality of notches, arms and feet is connected to an output of the gearbox. A drive shield is placed around a rearward side of the sweep wheel that forms a channel that is configured to capture grain agitated by the drive wheel. A guide plate is connected to the gearbox and covers a portion of the gearbox. The guide plate angles from an upper outward edge downward and forward to a lower inward edge that is configured to urge the grain captured within the channel of the drive shield to move in front of the sweep auger system reducing grain left in the grain bin.

Method and system for controlling at least one electrical machine

Abstract: A method and a system for a vehicle comprising: one or more power sources including at least one electrical machine; and a drivetrain for transferring torque between the one or more power sources and at least one drive wheel of the vehicle. The method comprises: controlling, when no positive drive torque (Tdrive) is transferred from the drivetrain to the at least one drive wheel, the at least one electrical machine to provide a backlash torque (Tbacklash) to the drivetrain, the backlash torque (Tbacklash) having a controlled value for turning the drivetrain if there is a backlash present in the drivetrain.

All-terrain explosion-proof traction transport vehicle for special mine

Abstract: The utility model discloses an all-terrain explosion-proof traction transport vehicle for a special mine. Wherein the lamp holder (1), the miner lamp (2), the radiator (3), the covering plate (4), thedirection control rod (5) or the steering wheel (27), the explosion-proof engine (6), the wet clutch (7), the gearbox operating handle (8), the seat (9) and the rear carriage (23) are arranged on theupper portion of a frame body, and the front and rear triangular crawler-type walking mechanisms are arranged below the frame body. The crawler-type walking mechanism is provided with a gearbox (45),a transmission shaft (16) connected through the gearbox (45) and a universal joint (15), a drive axle in drive connection through the transmission shaft, a drive wheel in drive connection through thedrive axle, a brake cylinder, a brake inner disc, a brake transmission shaft, a tensioning wheel (14), a main thrust wheel (11), an auxiliary thrust wheel (12) and a crawler belt (10). The mining transport vehicle meets the requirements for flexibility, high efficiency and multi-working-condition operation, is reliable in performance and high in applicability, and greatly improves the mine operation efficiency.

Method and drive assembly for operating a rail vehicle

Abstract: The invention relates to a method for operating a rail vehicle comprising the following steps: a) detecting at least one signal at a component of a drive train (1) of the rail vehicle, wherein it is possible to determine a torque applied in the drive train (1) from the at least one signal, b) determining a torque curve on the basis of a plurality of successively detected signals, c) determining a slip at at least one drive wheel (24, 25) of the rail vehicle on the basis of the torque curve determined, d) storing data representing the torque curve in a data memory (23) of a control device (21), and e) evaluating the data for the purpose of determining the service life, determining wear and/or planning maintenance for at least one component of the drive train (1). Furthermore, the invention relates to a corresponding drive assembly which is suitable for carrying out such a method.

Few-drive wheel leg type composite robot for planet detection

Abstract: The invention relates to a few-drive-wheel leg type composite robot for planet detection, and belongs to the field of planet detection composite robot design The robot comprises a robot body, a waistunit, four wheel-leg mechanisms, two single-leg mechanisms and a wheel driving unit, wherein the robot body is of a plate-shaped structure which is horizontally placed; the waist unit is fixedly mounted on the lower surface of the robot body; the two single-leg mechanisms are symmetrically installed at the two ends of the waist unit; every two of the four wheel-leg mechanisms are symmetrically distributed; the four wheel-leg mechanisms are respectively connected with four end parts of the waist unit; and the wheel driving unit is fixedly mounted in the middle of the bottom of the waist unitAccording to the invention, the robot is driven by a small number of motors, and foot-type walking and wheel-type driving of the robot and rapid switching between multiple driving modes are realized by utilizing a leg connecting rod mechanism configuration transformation and the active and passive wheel-type driving units

Six-freedom-degree swing frame type wheel assembling machine and assembling method thereof

Abstract: The invention provides a six-freedom-degree swing frame type wheel assembling machine which comprises drive wheel systems, a vehicle body system, a left swing frame system, a right swing frame system,an electric control system and a hydraulic station. A U-shaped vehicle body in the vehicle body system is connected with connecting plates in the drive wheel systems. A first hinge and a second hingeof the vehicle body system are connected with a first overhanging beam in the left swing frame system and a second overhanging frame in the right swing frame system correspondingly. The electric control system and the hydraulic station are installed in the U-shaped vehicle body. The wheel assembling machine comprises six freedom degrees including moving in the axis direction of wheels, moving inthe direction perpendicular to the axis, spot turning, rotation around wheels and front-back pitching swinging of the wheels. By means of the six-freedom-degree swing frame type wheel assembling machine, assembling mechanization of wheels of heavy mining dump trucks can be achieved, the labor cost is reduced, and the labor intensity of workers is lowered; and the assembling efficiency of the wheels of the heavy mining dump trucks is improved, and the installation quality consistency and the production takt are ensured.

Container type lifting express box unmanned distribution vehicle

Abstract: The utility model discloses a container type lifting express box unmanned distribution vehicle. The unmanned distribution vehicle is matched equipment of a lifting express box distribution system. Thelifting express box is conveyed to the position below the lifting device through automatic driving. DISTRIBUTION VEHICLE HAVING A VEHICLE BODY PART, the bearing part is used for stacking express boxes; drive wheel, the control mainboard in the driving bin is provided with an automatic driving module and a wireless communication module; wireless connection interaction with a cloud background, a distribution center and a lifting device can be carried out; auxiliary positioning assembly, positioning detection is carried out through the positioning assembly; rEAL-TIME ADJUSTMENT BY WIRELESS INTERACTION, secondary accurate auxiliary positioning is realized; the unmanned distribution vehicles are adopted as distribution vehicles and recycling vehicles, chain type alternate alternation is conducted, and connection type distribution and replacement of distribution and recycling of the lifting express boxes are completed. The unmanned distribution vehicles are adopted as the distribution vehicles and the recycling vehicles.

Toy device for dispensing stackable or rollable materials and related methods

Abstract: A toy device for dispensing stackable or rollable materials and related methods are described The device has a housing (12) arranged to contain a stack or roll of material and having a dispensing aperture (30) A manually actuated drive mechanism (80) is provided by which a user can rotate a drive wheel (84) of the drive mechanism The drive wheel (84) contacts and when rotated engages a portion of the material and to drive it through the dispensing aperture (30) A release mechanism (60) is provided that can be moved to allow the material to be driven through the aperture (30) The drive mechanism can be actuated independently from the release mechanism

Using the Brake Torque to Redistribute the Engine Power Transmitting to the Left and Right Drive Wheels

Abstract: The automotive differential is a mechanism that splits the engine power to the two drive wheels into the left and right sides of the drive axles and allows the driven wheels of a vehicle to have different speeds while they are turning. When a vehicle moves straight on the same road friction at the two drive wheels, the differential applies the same amount of power to each drive wheel. However, if one of the drive wheels rolls on the skid road, the differential splits more the engine power to this wheel. As this wheel slip on the roads, the engine power is dissipated due to the friction between the road and tire. The solutions to this problem are using the limited-slip differential, the active differential. They allow more power to transmit to the non-slipping wheel. In this paper, the authors use the braking torque applied to the slipping wheel to redistribute the engine power on two drive wheels and design a controller based on the PID controller for traction control. The simulation result shows the efficacy of the designed controller.

Heat pump compressor heating device driven by wind energy

Abstract: The invention relates to a heat pump compressor heating device driven by wind energy. The heat pump compressor heating device driven by wind energy comprises a fan unit and a fan drive unit which aremutually connected, wherein the fan unit and the fan drive unit are connected with a heat pump heating unit separately; the fan unit comprises a fan drive wheel and a wind speed increaser which are mutually connected; the fan drive unit comprises a driven wheel and a motor which are mutually connected; the driven wheel is in engagement connection with the fan drive wheel; the motor is mechanicallyconnected with the wind speed increaser; the heat pump heating unit comprises a heat pump compressor; and the heat pump compressor is connected and arranged between the motor and the wind speed increaser. Compared with the prior art, the heat pump compressor heating device driven by wind energy is high in environmental influence adaptation capacity, and solves the technical awkward situation of no heat supply in the case of no wind.

Sucker type snakelike curtain climbing robot

Abstract: The invention discloses a sucker type snakelike curtain climbing robot and relates to the technical field of climbing robots Multiple vacuum suckers are fixed to the periphery of a fixing frame Eachabove running climbing mechanism is composed of a driving mechanism, a drive wheel and a driven wheel, wherein the driving mechanism comprises a motor and a speed reducer, the motor is fixed to the fixing frame, an output shaft of the motor is connected with the input end of the speed reducer, the output end of the speed reducer is connected with the drive wheel, and the driven wheel is rotationally connected to the fixing frame through a wheel axle By means of the curtain climbing robot based on a vacuum suction assembly, the moving speed is ensured, meanwhile, a mooring rope does not needto be used under manpower to move the robot, the capability that the robot is adsorbed on a work surface is achieved, due to a rotating obstacle crossing joint mechanism, the obstacle crossing and turning functions of the curtain climbing robot are better achieved, meanwhile, the weight of the climbing robot is greatly reduced, and portability is improved

Adjusting device and door closer assembly

Abstract: The invention is related to an adjusting device for a door closer This adjusting device comprises a worm screw (1) intended to be engaged with the door closer, a drive wheel (3) solidly attached to the worm screw (1), a connection element and an indicator wheel (6) The connection element comprises a first wheel (4) meshed with the drive wheel (3) and a second wheel (5) which is solidly attached with the first wheel (4) The indicator wheel (6) is meshed with the second wheel (5) The invention also provides a door closer including such an adjusting device

A drive arrangement for a floor surfacing machine and a floor surfacing machine

Abstract: A floor surfacing machine (100) comprising a planetary head (140) with one or more satellite heads (120), wherein a first drive motor (110) is arranged to drive the planetary head (140) via a drive arrangement (300, 300’) and wherein a second drive motor (130) is arranged to drive the one or more satellite heads (120), the drive arrangement (300, 300’) comprising:-a first drive wheel (310) arranged to be driven by the first drive motor (110), and -a second drive wheel (330) fixedly attached to the planetary head (140) and arranged to be driven by the first drive wheel (310),wherein the second drive wheel (330) is arranged radially inwards from a first motor axle (111) of the first drive motor (110) relative to a rotational axis of a second motor axle (135) of the second drive motor (130), and wherein the second drive wheel (330) is provided with a central aperture encircling the second motor axle (135), and the second drive wheel (330) being arranged coaxial with the second motor axle (135) and arranged rotatable relative to the second motor axle (135).

Specimen clearing apparatus

Abstract: The present disclosure relates to a device which automatically clears high elongation test samples with long tails after breakage from a materials testing device after the testing has been performed. A robotic arm engages the tested specimen and brings it to a specimen clearing device which includes a slot leading to a nip between an opposed drive wheel and driven wheel. A motor drives the drive wheel to move the tested specimen through the specimen clearing device into a scrap bin or similar repository.