723 results about "Dynamic positioning" patented technology

The system is an integrated and self contained electric thruster system integral with a dynamic positioning control system for dynamic positioning of any waterborne vessel having a hull with at least two sides and a deck connecting the sides, at least two azimuthing thrusters, each removably mounted to the vessel, at least two self-contained electric power units removably secured to the deck, one for each thruster, at least one dynamic positioning computer connected to each of the self contained electric power units, at least one motion reference sensor connected to the dynamic positioning computer to correct reference position signals for motion of the vessel, at least one heading sensor, and at least one sensor that is either a position reference sensor connected to the dynamic positioning computer, environmental sensors connected to the dynamic positioning computer, or a combination thereof.

The invention discloses a charging and battery replacing monitoring system and method based on internet of things. The system comprises terminal information acquisition equipment, charging and battery replacing monitoring equipment and area monitoring equipment, wherein the terminal information acquisition equipment is used for carrying out identity identification, state information acquisition and dynamic positioning on terminal equipment by utilizing an information sensing mode, transmitting identity identification information to the charging and battery replacing monitoring equipment through a wireless network, and transmitting the state information and the positioning information to the area monitoring equipment through the wireless network; the charging and battery replacing monitoring equipment is used for receiving the identity identification information of the terminal equipment, monitoring the working state of a charging and battery replacing station, metering and charging the charging and battery replacing process, and transmitting the state information of the charging and battery replacing station, the metering and charging information and the identity identification information to the area monitoring equipment; and the area monitoring equipment is used for monitoring the terminal equipment and the charging and battery replacing station in a jurisdiction area and making a statistics on the metering and charging information. Through the system and the method disclosed by the invention, concentrated monitoring and management on the terminal equipment and the charging and battery replacing station can be carried out.

The present invention is a method and apparatus that provides detection, characterization, and intuitive dissemination of targets. This disclosure combines improvements to ultra-wideband (UWB) sensing and machine target characterization with a means to convey data in a format that is quickly and readily understood by practitioners of the technology. The invention is well suited for Situational Awareness (SA) support in areas that are occluded by rain, fog, dust, darkness, distance, foliage, building walls, and any material that can be penetrated by ultra-wideband RF signals. Sense Through The Wall (STTW) performance parameters including target range, stand-off distance, and probability of detection are improved herein by combining a dynamically positioned sliding windowing function with orthogonal feature vectors that include but are not limited to time amplitude decay, spectral composition, and propagation time position in the return signal data. This invention is particularly useful for STTW and SA applications including urban combat, law enforcement, fire protection, transportation security, and homeland security. The invention can also be used to detect objects that are concealed by clothing, debris, and other non-metallic materials.

The invention discloses an unmanned aerial vehicle system and a method for dynamically positioning a ground moving target, belonging to the fields of unmanned aerial vehicle system application and the like. The unmanned aerial vehicle system comprises an unmanned aerial vehicle body, a vehicle-mounted photoelectric rotating tower and a ground control terminal, wherein the unmanned aerial vehicle body comprises an acquisition device, the vehicle-mounted photoelectric rotating tower comprises a photoelectric sensor and a sight-stabilizing platform, and the ground control terminal comprises a determining device, a trace command generating device, a resolving device and a predicting device. According to the technical scheme provided by the invention, geographical coordinate information including latitude, longitude and the like of a tracked ground moving target can be output in real time, the original geographical coordinate information can be accurately and quickly fitted, the moving trend of the ground moving target can be predicted and evaluated, and the original geographical coordinate information can be screened to realize display and prediction of the track of the moving target; the positioning accuracy acquired by the unmanned aerial vehicle system and the method approaches that of static positioning and can meet requirements for initial alignment of weapons including artilleries and the like, and the probability of fusion processing of an unmanned aerial vehicle intelligence system and an entire-army intelligence gathering network is provided.

The invention discloses a concrete pouring and vibrating dynamic visualization monitoring method. A vibrating bar point operating track detecting system based on global position system (GPS) dynamic positioning test collects / transfers / processes vibrating bar point operating track state parameter information in real time and adopts a computer graphic on-line method to display, and monitors and evaluates pouring and vibrating state effect in real time according to judge standard of concrete vibrating control parameters (such as vibrating geometric boundary / vibrating effective radius / vibrating inserting-and-extracting threshold and the like). Therefore, phenomena including vibration omission / vibration lack / excessive vibration, construction cold joints and the like are avoided, accurate quantization judge of the concrete pouring and vibrating density state is achieved, a traditional method that the concrete pouring and vibrating state is completely judged by on-site operators relying on experiences is thoroughly changed, the shortcoming that on-site concrete vibrating below the standard is difficult to process and poor in processing effect is overcome, and vibrating construction defects can be processed accurately and reliably.

The invention discloses a multi-system dynamic PPP resolving method based on robust self-adaption Kalman smoothing. The method includes the steps that receiving machine outline coordinates and receiving machine clock bias of all systems are solved through selecting-weight-iteration pseudo-range single-point positioning, and accordingly all positioning error correction values are calculated according to an error correction model in combination with the satellite precise ephemeris and satellite precise clock bias; strict data quality control is conducted on observation data. Due to the fact that dynamic PPP accuracy is easily affected by undetected small cycle slips or the gross error and the like, an observation equation weight matrix is adjusted according to the observation value residual vectors, and the undetected small cycle slips or the gross error and other influence factors are removed; self-adaption factors are determined according to the state predictive information, and thus the influence on parameter estimation of the predictive information is controlled. By means of the method, when multi-system dynamic PPP is conducted through a single receiving machine, the feature that the number of multi-system satellites is increased greatly, on the basis that the stability of the satellite structure is guaranteed, the influence of the gross error is weaken effectively, the dynamic noise abnormity in dynamic positioning is improved, and finally the high-precision and high-stability multi-system dynamic PPP result is achieved.

A fleet of vessels attached together longitudinally (rows), and transversely (columns) and operating in unison convert wave energy to electrical energy which is stored in either a chemical or electrical form. The vessels when detached from the fleet provide transportation to coastal or by navigable waterway ports of call for distribution to market centers. Both wind wave and swell wave energy conversion is performed by use of the differential motion between the vessels. Means are provided for the energy conversion systems to adapt to changes in wave direction, wave length, amplitude, and phase. Such vessels are self powered for off shore or inland waterway navigation, either singularly or in multiples, with which to deliver energy to other sea going vessels or to land based ports of call. Two or more of such vessels are capable of using the energy of waves during the delivery process. The fleet can maintain a designated geographical location by dynamic positioning. Alternatively, the fleet may maintain its designated position by moorage of a designated centrally located vessel in the fleet to a permanent anchoring system when operating at appropriate depths.

The invention discloses an indoor personnel positioning system and an indoor personnel positioning method based on path rule and prediction, and in particular relates to a wireless sensor network indoor people and object positioning system and a wireless sensor network indoor people and object positioning method. The system comprises a positioning control center, positioning information integration equipment, reference node equipment and unknown node equipment. According to the method, a PC (Personal Computer) and the positioning system are adopted to perform indoor people and object positioning through a program and based on a wireless network after a system preparatory stage and a system operating stage. The system and the method have the characteristics of high positioning accuracy, high positioning precision, wide applicable scope, high applicability, simpleness in operation, convenience for promotion and application and the like. The system and the method can be widely applied to indoor personnel static and dynamic positioning, and is also applicable to indoor object static and dynamic positioning.

The invention provides a robust self-adaptive track tracking control system for a dynamic positioning vessel. A position and angle sensor acquires and then sends actual positions and course angles, and reference positions and reference course angle information, which are generated by a reference path generator, to a neural network estimator and a second-order sliding mode observer and obtains a model unknown non-linear function estimation value and state estimation value and then transmits the state estimation value to a disturbance estimator and a diffeomorphism convertor at the same time and obtains an interference estimation value and a new state variant respectively. All of information obtained by the neural network estimator, the second-order sliding mode observer, the interference estimator, the diffeomorphism convertor and the position and angle sensor is transmitted to a controller and a control instruction is resolved to drive an execution mechanism and realize track tracking of a water-surface vessel. The robust self-adaptive track tracking control system for the dynamic positioning vessel does not need known precise hydrodynamic-force parameters of the water-surface vessel or precise identification of inertial mass parameters and realizes track tracking of the dynamic positioning vessel under a condition that interferences from an unknown environment exist.

Techniques are provided for providing automated configuration of computing devices. More particularly, principles of the invention may use anticipated context to precondition a device whose operational mode is alterable via computer controllable operations. Anticipated context may be affected by any number of parameters including, but not limited to, current location, time of day, destination end-point, e.g., phone number to be called, past history, subscription rate plans, power requirements of device, application demands with respect to quality-of-service (QoS), security, calendar information, and so on. Further, principles of the invention may use locally derived knowledge about the intended use of a device and dynamically enable it in a desirable mode of operation using locally reachable configuration parameters stored in advance based on the anticipated context for the operation of the device. Still further, principles of the invention may dynamically locate necessary configuration parameters via a service discovery process.

A method and an apparatus for dynamic targeting for a process control system. A process step is performed upon a first workpiece in a batch based upon a process target setting. The process target setting comprises at least one parameter relating to a target characteristic of the first workpiece. Manufacturing data relating to processing of the first workpiece is acquired. The manufacturing data comprises at least one of a metrology data relating to the processed first workpiece and a tool state data relating to the tool state of a processing tool. Electrical data relating to the processed first workpiece is acquired at least partially during processing of a second workpiece in the batch. The process target setting is adjusted dynamically based upon a correlation of the electrical data with the manufacturing data.

The invention discloses a dynamic positioning method and device based on UWB and laser ranging combination and belongs to dynamic positioning methods and devices. The dynamic positioning device comprises an ultra-wide band (UWB) wireless communication sensors, a UWB positioning label, laser ranging sensors, an upper computer and a POE interchanger. An ultra-wide band (UWB) wireless communication sensor station is arranged in an area to be detected, the laser ranging sensors are installed on and fixed to the ultra-wide band (UWB) wireless communication sensors, the UWB positioning label is fixed to a target to be detected, and the ultra-wide band (UWB) wireless communication sensors and the laser ranging sensors are connected with the upper computer through the POE interchanger. According to the dynamic positioning method and device based on the UWB and laser ranging combination, the laser ranging sensors are arranged on the ultra-wide band (UWB) wireless communication sensors respectively, so that the relative distance between every two adjacent ultra-wide band (UWB) wireless communication sensors is obtained, in this way, the coordinates of the ultra-wide band (UWB) wireless communication sensors can be re-determined or corrected after the ultra-wide band (UWB) wireless communication sensors are moved, and thus the requirement for dynamic positioning is met. The dynamic positioning method and device based on the UWB and laser ranging combination have the advantages that the dynamic positioning method based on the UWB and laser ranging combination is adopted, positioning is accurate, safety and reliability are guaranteed, installation is easy, and operation is convenient.

The invention provides a positioning method and device, belonging to the field of wireless communication application. The method comprises the following steps: acquiring a wireless signal in an unknown position; acquiring the signal intensity of the wireless signal and an identification code ID of a preset beacon node to which the wireless signal belongs; processing the beacon node ID and the signal intensity to obtain the characteristics of the unknown position; acquiring a coordinate of a last position of the unknown position; removing the grids divided in a positioning region in advance according to the coordinates of the last position; sorting the grids in the positioning region by utilizing a support vector machine; acquiring barycentric coordinates of the designated grids which are sorted at the top; and obtaining the coordinates of the unknown position by calculation. The positioning method and device provided by the invention do not need to measure the distance, thus the distance measuring error can not be generated, the precision in positioning is high, the influence degree by the signal is low, and the correlation between the last position and the current position in the dynamic positioning process can be reflected, thus decreasing the positioning error.

The invention discloses a graded positioning method for agricultural machinery navigation, comprising the following steps of acquiring a first positioning parameter, utilizing a Kalman filter to fuse the first positioning parameter, acquiring a second positioning parameter, acquiring a third positioning parameter, utilizing multi-sensor self-adaptive weighted fusion algorithm to fuse the second positioning parameter with the third positioning parameter, acquiring a target positioning parameter and positioning agricultural machinery according to the target positioning parameter. The invention also discloses a graded positioning system for agricultural machinery navigation. By fusing the positioning parameters acquired by measurement equipment for a plurality of times, the graded positioning method can smooth DGPS positioning data, effectively avoid the abnormal results of DGPS dynamic positioning, effectively filter test noise, reduce systematic error, form continuous, stable and accurate the information of the positions and course heading angles of agricultural machinery, and improve the positioning accuracy of agricultural machinery navigation.

An improved catheter insertion assembly having a transparent tubular member open at each end; a plunger assembly slidable within the tubular member having a stem portion at a first end; and at least a partially transparent chamber having a needle base and sealing member on a second end of the plunger assembly; an elongated tubular needle embedded within the needle base and extending there from with the needle in fluid communication with the transparent chamber; a catheter assembly, a transparent cannula and a transparent hub attached to the second end with the tubular needle passing longitudinally through the cannula; a fluid passage formed between the needle and the cannula so that when the plunger is retracted a vacuum is established within the fluid passage and blood is visibly drawn through the fluid passage into the transparent cannula and if volume permits, blood then would be visible in the transparent hub, and then if volume permits blood would be visible in the void of the catheter body (barrel) created by pulling the plunger; and wherein the tubular needle is threaded through a lumen of the cannula; and wherein the sealing member provides a sliding seal between the plunger assembly and the transparent tubular member; and wherein, a fluid communication exists through the needle into the flashback chamber of the plunger apparatus and through a porous vent. The distal end of the catheter device described herein has the addition of an external flange and dual plunger paddles which allow dynamic positioning of the fingers and one handed operation. Furthermore these structures are ergonomically associated to maximize finger surface area operation; and wherein the user can change the orientation of the beveled needle.

The invention discloses a path tracking guiding control method of a dynamic positioning ship. The path tracking guiding control method of the dynamic positioning ship comprises the steps that (1) a geodetic coordinate system, a hull coordinate system and a mathematical model of the ship are built; (2) a guiding strategy is generated through by setting the geometrical position relation between a path generated by path points and the ship, and the expected heading of the ship at the current moment is calculated; (3) control moment needed by controlling the ship to achieve the expected heading is obtained through application of a control algorithm; (4) longitudinal thrust needed by controlling the ship to be at the expected movement speed is calculated. According to the path tracking guiding control method of the dynamic positioning ship, the expected heading, on a high-speed path tracking linear section, of the ship and the expected heading, on a high-speed path tracking turning section, of the ship are calculated according to track information and the relative position between the flight path and the ship, the movement speed of the ship is controlled through the longitudinal thrust, the calculation process is simple and easy to implement, and the path tracking guiding control method of the dynamic positioning ship is applicable to engineering application.

The present invention provides an improved architecture for integrating an inertial navigation system (INS) into a dynamic positioning (DP) system for a vessel. The architecture includes an INS unit and a DP system having a Kalman filter or other algorithm for combining data supplied by a plurality of position measuring equipment (PME) and the INS unit to derive an estimate of the position or speed of the vessel. A switch array and a switch array controller are also provided. These may optionally form a part of the DP system. The switch array is operable under the control of the switch array controller to supply data supplied by one or more of the plurality of position measuring equipment to the INS unit for the purposes of correcting drift. The selection of which of the one or more PME is / are to be combined with the INS unit is made automatically, in real time, to dynamically optimise the DP system.

The invention provides a semi-submersible type platform dynamic positioning model testing propulsive device, which belongs to the field of sea engineering. The propulsive device comprises a full circle swinging realization mechanism and a main transmission mechanism, wherein shafting of the main transmission mechanism is arranged inside the full circle swinging realization mechanism; a first bearing and a second bearing are arranged on an inner spindle; a first straight gear is arranged on a stepper motor, and is engaged with a second straight gear; the second straight gear is arranged on the upper end of an outer spindle; the outer spindle is provided with a pod and a conduit, and is connected in an outer shaft housing through a first thrust bearing and a second thrust bearing; and a third bearing is arranged on the end of the pod close to the end of a propeller. The propulsive device simplifies the shafting by adopting the main transmission mechanism and the full circle swinging mechanism, reasonably utilizes space, and ensures flexibility of the device. On the basis of not affecting operation of the main transmission mechanism, the propulsive device can realize omnibearing turning and omnibearing propulsion in 360 degrees, and improve response speed of a dynamic positioning propulsive system.

The invention provides a method of double terminal satellite positioning communication and central control and management for managing taxies, which comprises the steps of: (a) receiving requesting information from a user calling for a taxi; (b) obtaining the information of the taxi, a map and the user; (c) analyzing and making a simulative dynamic positioning strategy according to the information of the taxi, the map and the user and choosing one or a plurality of managing proposals according to the simulative dynamic positioning strategy; (d) sending the requesting information of booking to corresponding taxi client terminals according to the managing proposals; (e) feeding back the answering information sent from the taxi client terminals; and (f) providing the wireless talking back and calling function when the taxi arriving at the surrounding area of the user. The method and the taxi with the automatized booking requesting and managing and precise positioning are closer to daily communication and thinking modes and solve the problems that a user can not find a taxi and an empty taxi can not find a user. The invention also discloses a system of double terminal satellite positioning communication and central control and management for managing taxies.

The invention relates to a dynamic positioning and scheduling method and system, which integrate satellite positioning, a digital map and a GIS (Geographic Information System) into a whole and are suitable for real time positioning and scheduling of fleets. The dynamic positioning and scheduling method comprises the following steps of: presetting a parameter required by dynamic positioning and scheduling; carrying out road matching algorithm processing according to GPS (Global Positioning System) positioning information and the GIS; setting each fleet as one category; calculating the positionwhere the fleet arrives every X seconds within 0-T min; judging whether the fleet deviates a preassigned path; judging whether other fleets are in a safety car distance value L0; if not, sending alarming information; judging whether the traveling average speed of the fleet is less than a set car speed value V0, if so, transferring to a standby path; judging whether the fleet arrives a destination, if so, clearing the fleet in the categories; repeating the steps until category operations of all fleets are completed. Therefore, by utilizing the dynamic positioning and scheduling method and system, the real time positioning and monitoring of a plurality of fleets can be realized, alarming can be given when conflict conditions occur, and intelligent command scheduling functions can be realized.

The invention discloses a laser three-point dynamic positioning method and a system thereof. The method comprises: two base stations which are a first base station and a second base station are arranged at the fixed positions; a main station is arranged on a moving object; the base stations transmit the laser to the main station; the base stations are connected with the main station by wireless communication; a base line is defined to be a connecting line between the first station and the second station; the first base station acquires the included angle alpha between the main station corresponding to the first base station and the base line, and the included angle beta between the main station corresponding to the second base station and the base line; the first and the second base stations respectively send the included angles alpha and beta to the main station; and the main station can determine the position of the main station according to the included angles alpha and beta as wellas the length L of the base line. The laser three-point dynamic positioning system is constructed according to the method. The technology can be used for locating the moving object in field operationin the environment without marks in a dynamic, and has the advantages of high locating accuracy, simple operation principle and low implementation cost.

The invention discloses a method and a device for generating a high-precision map without relying on RTK (Real Time Kinematic). The method comprises the following steps: acquiring picture data from acamera; acquiring point cloud data from the laser radar; acquiring attitude information from a Global Navigation Satellite System (GNSS) / Inertia Measurement Unit (IMU); processing the picture data toextract visual feature information, and performing pose estimation according to the visual feature information extracted from the current frame, previously fused overall pose information and previously maintained map visual feature information to obtain camera pose estimation; processing the point cloud data to obtain point cloud information, and performing attitude estimation according to the point cloud information and other information to obtain radar attitude estimation; fusing the attitude information, the camera attitude estimation and the radar attitude estimation to obtain a more accurate and stable attitude estimation result; and according to a more accurate and stable attitude estimation result, fusing the picture data and the point cloud data to construct a high-precision map.

The invention belongs to the technical field of the Internet of Things and provides a UWB-based TOF locating method. The method comprises the following steps: establishing a locating detection model in an upper computer according to a regional environment of a to-be-located mobile terminal and a distribution position of a UWB sensor; establishing a distance measurement model in the upper computeraccording to the arrangement position of a TOF ranging sensor; locating a UWB locating tag on the to-be-located mobile terminal via a TDOA algorithm, and displaying 3D coordinates and a real-time position of the region of the mobile terminal; (4) changing the position of a base station of the UWB sensor, measuring the distance by using the TOF ranging sensor, and marking the 3D coordinates of theUWB sensor again; and locating the to-be-located mobile terminal again. According to the UWB-based TOF locating method, by adoption of the advantages of the UWB technology, the distance is accuratelymeasured by using the TOF ranging, the response speed is high, the error is small, and the interference degree is small.

A thrust distributing method of a dynamic positioning system comprises the steps of dividing thrusters into several groups, and fixing relative angles of azimuth angles of the thrusters in each group but not fixing absolute angles; obtaining a thruster azimuth angle with slow change by a low frequency part of a control command by means of an optimization algorithm, and then thrust of the thrusters is obtained by means of the optimization algorithm, namely inputting a control command T [c , k] at the k moment into a low pass filter composed of a first-order inertial element, and then carrying out discretization to obtain the low frequency part T [k+1]; calculating the thrust fk of all the thrusters and the azimuth angles alpha k of all the thrusters from the control command T [c , k] by means of the sequence quadratic programming method; obtaining the thrust fk of all the thrusters by means of the quadratic programming method; and adding the thrust reduction coefficient p to a given objective function and part of formulas with constraint conditions. According to the thrust distributing method of the dynamic positioning system, the thrust and the azimuth angles of the thrusters can be calculated separately, and therefore errors and strange structures caused by linearization are avoided, and energy consumption of the thrusters is reduced.

The invention discloses an UUV four degree-of-freedom dynamic positioning adaptive anti-interference sliding mode control system and a control method. The system comprises a first differentiator, a second differentiator, an adaptive anti-interference sliding mode controller, a filter and data fusion unit, a Doppler sensor, an electric gyrocompass, a thrust allocation unit, an UUV, an accelerometer and a gyroscope , wherein the adaptive anti-interference sliding mode controller comprises a sliding mode controller, an adaptive disturbance compensation controller and a data processing unit; the sliding mode controller is used for realizing UUV four degree-of-freedom dynamic positioning variable structure control and eliminating pose errors; and the adaptive disturbance compensation controller is used for estimating uncertainty errors of an actually controlled object model and wave disturbance effects in an online mode. A dynamic process during which the system state approaches to the sliding mode surface is improved, steady-state anti-interference performance is improved, and compared with a common sliding mode control method, dynamic performance is better, and buffet of the system under disturbance effects can be reduced.

Dynamic positioning of a vessel 10 connected to the seafloor 14 by a riser 12 utilises a measurement of riser 12 bottom angle combined with a measurement of vessel 10 velocity, optionally obtained from a Doppler log 16. These two signals are combined to produce a single position estimate using an algorithm such as a Kalman filter. Using riser bottom angle only would result in an unstable control system, since the bottom angle lags the vessel motion by a considerable amount and the relationship is non-linear. Using the velocity measurement alone would result in a slow drift of position. The combination of the two eliminates the disadvantages of the individual measurements.

The invention relates to a deepwater semi-submerged drilling platform, which comprises floating tanks, an upright post, a transverse supporting rod and a main deck, wherein a drilling block is arranged above a moon pool in the middle of the main deck; and a derrick is arranged on the drilling block. The deepwater semi-submerged drilling platform is characterized in that: a half derrick space for pre-connecting a drilling tool is reserved on one side of the derrick; a water isolating pipe, a drilling stem, a blowout preventer and a production tree are arranged on the main deck around the moon pool respectively; and an anchor moored positioning and dynamic positioning combined position system which consists of front and back four groups of anchor gears distributed on the left and right sides of the main deck is adopted, each group of anchor gears are provided with 3 anchor chains, a dynamic positioning system consists of 8 dynamic thrusters capable of rotating 360 degrees at the front and back four corners of the bottom of the two floating tanks. In the deepwater semi-submerged drilling platform, the maximum operation water depth is up to 3,000 meters, the maximum drilling depth is up to 12,000 meters, and the maximum variable load is up to 9,000 tons. The deepwater semi-submerged drilling platform can operate in the South China Sea, Southeast Asian sea area and West Africa sea area with severe sea conditions efficiently and safely.

A touch-sensitive display surface having touch-capacitive and vibration sensors. This surface allows the user to rest their fingers on the keys of an onscreen keyboard and type as they would on a regular keyboard. As the user places their fingers on the touch screen, the system relocates the onscreen keyboard to the location where the fingers are resting. The touch sensors report the signal strength level of each key touched to a processor, but no keystroke is issued by the processor until a corresponding “tap” (i.e., vibration) is detected. When a tap is detected, the processor references the status of the touch capacitance sensors before, during, and / or immediately after the moment in time the tap occurred. The size, position, and orientation of the onscreen keyboard keys are dynamically set as determined by the user initiating a home-row definition event by resting their fingers momentarily on a virtual home-row.