Abstract: The device consists of a rigid pendulum (1) pivoted at its upper end (2) and upon which a ball (5) is retained at its lower end in a holder (6), so that the center of the ball lies on or close to the longitudinal axis of the pendulum. The holder itself is attached to a shoe (3) which pivots about a point (4) on a projection offset from the bottom end of the pendulum, such that the shoe moves in an arc which lies in a vertical plane perpendicular to the vertical plane in which the pendulum swings. Movement of the shoe about this pivot allows the ball holder (6) and thus the ball (5) to move in an approximately radial direction with respect to the pendulum pivot (that is, along the axis of the pendulum when the ball center is on that axis) and the degree of movement of the shoe about its pivot is limited by stops (7a, 7b) provided on the pendulum. The complete pendulum device is supported in a tripod framework or alternative rigid support.

Abstract: A method of characterizing and screening a disc drive based on a voice coil motor pivot friction developed during a low velocity seek operation consists of determining estimated drive level bias values required by the voice coil motor to move an actuator arm assembly during a fast seek, then determining a low velocity drive level bias values required by the voice coil motor to move an actuator arm assembly during a slow seek, then computing a difference between the estimate drive level bias values and the low velocity drive level bias values, then determining a hit counter value based on comparing the computed difference with a predetermined threshold value, and then characterizing the disc drive based on the hit counter value.

Abstract: Apparatus for measuring the static coefficient of friction (SCOF) of the surface of an operating conveyor belt comprises a friction roller rotatable about an axis perpendicular to the direction of movement of the conveyor belt, a friction roller actuator for moving the friction roller between a retracted disengaged position and an advanced engaged position, and a friction roller drive motor selectively operable, in one instance, for permitting free wheeling rotation of said friction roller when rotatably engaged with the conveyor belt and, in another instance, for rotating said friction roller about the friction roller axis in a direction opposite the direction of movement of the conveyor belt.

Abstract: A method for determining the lift and drag coefficients of a golf ball includes launching the ball along a flight path, measuring the velocity at two positions along the flight path, using the measured velocities to determine the coefficients of lift and drag. The step of measuring the velocity includes taking two images of the ball at the two positions, where the time interval between images at each position is less than about 0.01 seconds.

Abstract: A method and apparatus for continuously or repeatedly monitoring road surface friction utilizes a separate test wheel attached to a vehicle and in contact with a road surface and a device for detecting slippage of the test wheel resulting from applying either a braking or accelerating torque on the test wheel. A signal corresponding to the applied braking or accelerating torque at the moment slip is detected and used to provide an indication to the driver of the slip condition. The method and apparatus is useful in vehicles as well as aircraft or in other applications where it is desired to monitor road friction. An embodiment of the invention applies and maintains a measured vertical force to the surface of the test wheel of the friction monitor utilizing an electromagnetic force field under processor control. The processor can combine signals from the vertical force torque motor circuit, and the test wheel torque motor circuit.

Abstract: A system is provided wherein road surface friction is sensed by measuring strain on a structure of a vehicle in a vicinity of a wheel of the vehicle. A road surface friction coefficient is determined by measuring strain on a structure of the vehicle in the vicinity of the wheel to produce signal outputs proportional to road surface frictional force and vertical load, and calculating the road surface friction coefficient from the outputs.

Abstract: Provided is a road surface friction coefficient measuring method and device for measuring the friction coefficient of road surfaces such as roads and runways, and which can be used by being mounted on a general car. This device has a spindle 5 detachably connected to the wheel of a travelling wheel 3 of a car, a support arm 6 oscillatably connected to the spindle, and a measuring wheel supported rotatably by the support arm.

Abstract: A friction test apparatus provided with a rotating friction means having an endless belt set around one pair of rotating drums, a belt supporting means disposed near an inner face of the belt, a sample holder to which a sample is detachably attached, and a sample holder driving means which holds the sample holder as to be rotatable and by which the sample attached to the sample holder is pressed to and part from an outer face of the belt. Further, the friction test apparatus is also provided with a meandering prevention mechanism which prevents the belt rotated by the pair of rotating drums from meandering.

Abstract: When a seal is inserted onto a shaft, load applied to a chuck is detected by a load cell, and based on the detected load, the turnover of a lip is judged. More specifically, an operation of inserting and pulling out the seal is performed several times on the shaft. Pull-out force is detected at the time of the last pull-out operation and insertion force is detected at the time of the last insertion operation. If the detected value is greater than a predetermined value, it is judged that the lip has been turned over. Also, a ratio between the aforementioned pull-out force and insertion force is computed. If the value of the computed ratio is less than a predetermined value, it is judged that the lip has been turned over.

Abstract: A method and apparatus for start-stop testing magnetic heads and hard disks in real disk-drive environment is provided. The tester has essentially the same dimensions as a conventional disk drive so that rotation of the disk pack inside the tester housing generates the same aerodynamic conditions as in a real disk drive. An accurate head positioning system, the operation of which does not depend on the deterioration of the magnetic conditions of the head and disk, is located inside the tester housing, and the friction and sticking forces can be measured till the moment of physical crash inside the housing. An essential advantage of the tester of the invention in that the measurement and positioning systems are combined into a single unit. The aforementioned combined system is based on the use of a Hall-effect sensor attached to the voice coil of the type used in the disk drive.

Abstract: A main-shaft malfunction-state detector in an air bearing type machine tool, in which an abnormal contact of a main shaft with a housing is reliably and automatically detected. The contacting state of the main shaft 11 and the housing 13 is detected through the presence of electric conductivity by a contact detection device 31. A contact decision device 32 determines the contact of the main shaft 11 with the housing 13 based on the detected conductivity, thus automatic and certain preventative measures, such as the main shaft of the machine tool stops and so on, are based on the above decision.

Abstract: A device for testing the take off speed of a thrust bearing in a disk drive spindle motor is disclosed. The device has a stationary torsion transducer that is used to support a drive shaft of the spindle motor. A load motor located adjacent to the transducer rotates the motor about the shaft while applying a radial load to the spindle motor through a belt. The load motor is attached to a linear stage which generates selected radial loads. In one version, the device also uses a ring magnet to attract the housing of spindle motor. The magnetic attraction imposes an axial force on the spindle motor and an equal reactive load on the thrust bearing. The axial load is such that the take off speed for the thrust bearing is much greater than that for the journal bearings. Under these conditions, the friction torque is dominated by the thrust bearing so that an accurate assessment of its quality may be assessed. As an alternative to the magnet, air jets may be used to apply a similar axial load to the thrust bearing.

Abstract: A friction testing machine and method for measuring friction characteristics between a test sample and a friction surface. The machine and method are particularly suited for measuring the coefficient of friction between a rubber specimen or a tread element and different friction surfaces at different sliding velocities, contact pressures and orientations. A preferred embodiment of machine is self-contained and portable, configured for easy and quick changing of the friction surface, and provides for rotating the test sample about an axis normal to the sliding surface and the direction of movement of the sample relative to the friction surface. In general, a friction test machine according to the invention comprises a sample holder configured to hold a sample in frictional engagement with a friction surface, and a motion device for effecting relative movement between the friction surface and sample holder in a first direction.

Abstract: An automated tribometer for measuring the coefficient of friction of the tread and gauge surfaces of railroad rail is disclosed. A tribometer is provided that is pushed in front of a high-rail vehicle, wherein during operation, the tribometer extends a rail test assembly to contact the surfaces of the rail. The rail test assembly has a rail testing wheel that is urged towards contact with the rail to be tested, and eventually contacts the rail, and lastly applies a known load to the rail. The testing wheel is then dynamically braked to slow the testing wheel to the point of creepage. The automated tribometer then can calculate the coefficient of friction of the rail.

Abstract: Traction and/or friction testing apparatus is described having inter-engaging, rotating, traction surfaces, the surfaces being independently driven to generate traction or friction forces therebetween. A force measuring means is provided to measure the resulting traction or friction force. The apparatus is characterised in that all forces applying in the traction measurement loop are directly readable, or elastic, thus eliminating internal friction and allowing an accurate indication of the traction or friction force. The apparatus is particularly useful for measuring rolling/sliding traction and friction.

Abstract: A valve position controller tuning method avoids impact of friction in valve positioner tuning by building a dynamic model of a valve positioner from a monotonic open-loop response of a valve stem position to a change in valve position controller output. To this end, a model form is selected based on the type of pneumatic actuator and relay that controls valve flow modulating of member motion, and the valve position controller is operated in an open-loop mode. The method includes changing a valve position controller output signal to cause the valve positioner to move a valve flow modulating member, connected to valve positioner, monotonically from one stuck position to another stuck position immediately after a motion in that same direction. When a valve stem position reaches a position threshold, a first valve stem position change and a corresponding time change are measured. The method includes measuring valve stem position changes at times that depend on the first measured time change.

Abstract: A method for measuring damping characteristics of a friction member include: relatively pressing a first member as a friction member to be measured against a second member, for relatively sliding with respect to a second member and vibrating, measuring vibration states of the pressed first and second members, and measuring variations in the vibration states of the pressed first and second members and measuring damping characteristics of the friction member to be measured against vibrations by comparing damped amounts based on the variations in the vibration states of the first and second members. The above method and an apparatus therefor enable detailed evaluations of friction member having high performance.

Abstract: A measurement apparatus and method for determining the traction and coefficient of friction of a material on a roller. First and second rollers transport the material. Encoders are coupled to each roller, and a motor is coupled to one of the rollers. The motor applies a forward and reverse torque to the first roller, wherein the material slips relative to the roller. A computer coupled to the encoders calculates the traction and coefficient of friction.

Abstract: A method and apparatus for operational monitoring of an actuator, which has a drive force unit that requires a characteristic time for build-up of the force, the apparatus including at least one position signal generator detecting a rest position of the actuator, a drive switch unit for actuating the drive force unit, and signal connections to an analyzing arrangement having a memory and a comparison unit so that, during operation, the time difference between the actuation of the drive switch unit and the possible response of the position signal generator allocated to the preceding rest limit position of the actuator is monitored, a comparison of the measured quantity to characteristic data deposited in the memory is implemented and a conclusion about the condition of the actuator is obtained from this analyzation.

Abstract: A horizontal plane frictional coefficient testing apparatus and methods are provided which include a substantially horizontal planar platen having two spaced, parallel movable rails. The rails are actuated by a motor adapted for reversibly raising and lowering the rails relative to the platen. A sled of predetermined weight is also provided having a central body and two pairs of outwardly extending axles, with each pair of axles being of equal length and formed with a wheel at the end thereof. The wheels of the sled are formed for engagement with the rails and engagement of the wheels with the rails locates the sled generally parallel to the rails. In operation, a sample of sheet material is fixed to the sled and the sled is placed on the rails, with the rails being in a raised position. Subsequently, the rails are lowered to gently place the sled onto the platen or a test medium fixed to the platen.

Abstract: A horizontal plane frictional coefficient testing apparatus and methods are provided which include a substantially horizontal planar platen having two spaced, parallel movable rails. The rails are actuated by a motor adapted for reversibly raising and lowering the rails relative to the platen. A sled of predetermined weight is also provided having a central body and two pairs of outwardly extending axles, with each pair of axles being of equal length and formed with a wheel at the end thereof. The wheels of the sled are formed for engagement with the rails and engagement of the wheels with the rails locates the sled generally parallel to the rails. In operation, a sample of sheet material is fixed to the sled and the sled is placed on the rails, with the rails being in a raised position. Subsequently, the rails are lowered to gently place the sled onto the platen or a test medium fixed to the platen.

Abstract: The invention is directed to an improved tribometer used to measure and test the interactions of two sliding bodies. The tribometer includes a sliding unit for holding the test samples, a unit for reciprocating a test sample, a signal conditioning unit for receiving a plurality of signals from sensors and a data acquisition and control unit which receives the signal data and sends control instructions to the sliding unit and to the reciprocating unit.

Abstract: When a seal is inserted onto a shaft, load applied to a chuck is detected by a load cell, and based on the detected load, the turnover of a lip is judged. More specifically, an operation of inserting and pulling out the seal is performed several times on the shaft. Pull-out force is detected at the time of the last pull-out operation and insertion force is detected at the time of the last insertion operation. If the detected value is greater than a predetermined value, it is judged that the lip has been turned over. Also, a ratio between the aforementioned pull-out force and insertion force is computed. If the value of the computed ratio is less than a predetermined value, it is judged that the lip has been turned over.

Abstract: A control apparatus for a motor-driven vehicle driven by a motor brakes the vehicle without giving shock to the vehicle. The control apparatus includes a vehicle maneuvering section for sensing a manual driving force as applied to it. The control apparatus also includes a control circuit which, when a manual driving force for driving the vehicle is applied to the maneuvering section, causes the motor to provide a mechanical driving force for the vehicle in accordance with the sensed manual driving force. The control circuit includes a braking force providing device which gradually increases a braking force for braking the vehicle from zero when manual driving force has been removed from the maneuvering section.

Abstract: The testing apparatus serves to measure the coefficient of friction of a golf ball. The apparatus has a base with a pair of flexure arms which carry inserts between which a golf ball may be pushed under a force in order to flex the flexure arms outwardly. Strain gauges record the flexing of the flexure arms in order to determine the force perpendicular to an insert. A load cell is employed to determine the amount of pushing force on the golf ball in order to determine a force parallel to the surface of the insert. The ratio of the two forces obtained serves as the coefficient of friction of a golf ball.

Abstract: A frictional dynamic characteristic measuring apparatus for measuring a pressing force and a frictional force acting between a friction material as a specimen and a slide portion which are in sliding contact, includes a sliding speed changing device for forcibly changing a sliding speed of the friction material and the slide portion, which is changing in a self-excited manner at a resonance frequency of a resonance system including the friction material and the slide portion, at the resonance frequency of the resonance system. This apparatus enables evaluation of a friction material which absorbs self-excited vibration in a torsional vibration system without the need of additional evaluation in an actual machine for use.

Abstract: An apparatus for determining a coefficient of friction on a surface of objects such as rails. In one embodiment, the apparatus comprises a vertical sensor assembly for determining the coefficient of friction of a top surface of a rail. A different embodiment comprises a lateral sensor assembly for determining a coefficient of friction of a gage face of a rail. The sensor assemblies may include a shoe. The sensor assemblies may include a load cell. Other embodiments include various combinations of lateral sensor assemblies and vertical sensor assemblies. Structure for mounting the assemblies to a vehicle may also be provided.

Abstract: An apparatus and method for detecting friction characteristics are disclosed, in which a wheel resonant system includes a vehicle body, a road surface and at least a wheel. A braking force control system exerts a braking force on the wheel. A resonant component detector determines a resonant gain providing the ratio between the amplitude of predetermined frequency component of the braking force and that of the wheel velocity and detects the ratio of the resonant gain to a present reference gain, a deviation calculator calculates the deviation between this ratio and unity, a PI controller controls the braking force control system in such a manner that the deviation coincides with zero, and a friction characteristics detector detects the friction characteristics on the basis of the braking force. When the friction force is made to approach a peak value by increasing the braking force, the resonant characteristics undergo a change thereby to reduce the resonant gain.

Abstract: Road surface frictional force is sensed by measuring the strain of a tire or the strain in the vicinity of a wheel of a vehicle, and the sensing of the road surface frictional force is part of an antilock braking system in which, cyclically, brake fluid pressure is increased when the road surface frictional force increases in response to increase of the brake fluid pressure and decreased when the road surface frictional force decreases despite increase of the brake fluid pressure and brake fluid pressure is increased again when the road surface frictional force decreases in response to decreasing of the brake fluid pressure.

Abstract: A modified SAE No. 2 friction machine is used to evaluate the clutch friction properties of motorcycle lubricants in a process comprising measuring the torque after a break-in period at three temperature points within the ranges 30.degree.-60.degree. C., 70.degree.-90.degree. C. and 110.degree.-150.degree. C. over a 10 second period while the speed of the motor driving the clutch plates varies from 0-300 rpm and the clutch plate pressure is held at 50 psi.

Abstract: A cylindrical, direct shear apparatus and method engage multiple layers of geosynthetic, geotechnical, or both types of materials for evaluating interface friction. Geosynthetic fabrics, geomembranes, naturally occurring materials (soils, rock, gravel, aggregate, other geotechnical materials), and the like maintain frictional contact in many applications. Conventional testing, as per ASTM standard D 5321-92 requires a comparatively modest displacement. Behaviors of geosynthetic membranes and geosynthetic fabrics may change substantially when displaced beyond the dimensions tested under ASTM standards. Accordingly, an apparatus for providing virtually unlimited displacement of layers under "normal" loading for establishing effective "displacement force" in order to establish an "effective coefficient of friction" over a range of displacements.

Abstract: The disclosure describes an apparatus for measuring the static and kinetic friction properties of sheet materials. The apparatus comprises a sled, moving table, means for creating and measuring the friction force between sled and table, and lift mechanism which places sled on table, and removes sled from the table. Novel aspects include a lift design which causes the sled to be maintained in positive contact with the force measuring means, friction force creating means which integrate a small displacement static forcing means with a mechanically stiff kinetic drive, and sled construction which securely clamps a flat test-piece on a flat plate.

Abstract: A friction testing machine and method for measuring friction characteristics between a test sample and a friction surface. The machine and method are particularly suited for measuring the coefficient of friction between a rubber specimen or a tread element and different friction surfaces at different sliding velocities, contact pressures and orientations. A preferred embodiment of machine is self-contained and portable, configured for easy and quick changing of the friction surface, and provides for rotating the test sample about an axis normal to the sliding surface and the direction of movement of the sample relative to the friction surface. In general, a friction test machine according to the invention comprises a sample holder configured to hold a sample in frictional engagement with a friction surface, and a motion device for effecting relative movement between the friction surface and sample holder in a first direction.

Abstract: Road surface friction is sensed by measuring strain on a structure of a vehicle in the vicinity of a wheel of the vehicle. Road surface friction coefficient is determined by measuring strain on a structure of a vehicle in the vicinity of a wheel of the vehicle thereby to produce signal outputs proportional to road surface frictional force and vertical load and calculating the road surface friction coefficient from the outputs.

Abstract: A main-shaft malfunction-state detector in an air bearing type machine tool, in which an abnormal contact of a main shaft with a housing is reliably and automatically detected. The contacting state of the main shaft 11 and the housing 13 is detected through the presence of electric conductivity by a contact detection means 31. A contact decision means 32 determines the contact of the main shaft 11 with the housing 13 based on the detected conductivity, thus automatic and certain preventative measures, such as the main shaft of the machine tool stops and so on, are based on the above decision.

Abstract: A method is provided for at least approximately determining the frictional value utilized between a wheel and the roadway. The method uses a vehicle weight that is determined, at least approximately, and a momentary actuating energy of a brake that is determined during a braking action. The method calculates the frictional value from the momentary actuating energy, the vehicle weight, and the wheel braking factor. In another embodiment, the method determines, at least approximately, the momentary vehicle deceleration. The frictional value is calculated from the momentary vehicle deceleration during braking and the Earth's gravitational acceleration.

Abstract: An apparatus for measuring a maximum static friction force is disclosed, in which the displacement of the relative positions of first and second objects due to the operation of a driving unit is suppressed for measuring an accurate static friction force characteristic.

Abstract: Apparatus and method for measuring the maximum static friction force and the kinetic friction force between the heads of a disc drive and discs adjacent the heads. The disc drive is rotated by a computer controlled spin-up motor which provides constant angular acceleration of the disc drive. Voltages at the ends of the windings of a spindle motor of the disc drive are sampled to detect the angular acceleration at which disc rotation relative to the heads begins, from which the static friction force and the kinetic friction force are determined. The angular acceleration of the disc drive is monitored through the sampling of velocity commands used to control the angular acceleration of the disc drive, or through the use of an accelerometer mounted with respect to the disc drive.

Abstract: A sensor system for measuring physical properties of paper. The paper property sensor system includes a surface and a diaphragm opposed to each other. The small diaphragm includes a first pair and a second pair p-type piezoresistors. Each piezoresistor of the first pair has a longitudinal axis and is located perpendicular to and very close to one of the long edges of the diaphragm. Each piezoresistor of the second pair has a longitudinal axis and is located between and parallel to first pair of piezoresistors, and away from the short edges of the diaphragm. Coupling the first pair of piezoresistors with the second pair via a Wheatstone bridge produces a voltage representative of the shear force exerted by a sheet.

Abstract: An oil seal tester having a moving shaft for engaging an oil sealing surface of a oil seal and at least one source of fluid to be applied against the moving shaft and against a first side of the oil seal. A force measuring device is used to measure the reaction torque exerted against the seal by the rotating shaft. Adjustments are provided for altering the shaft to bore misalignment and the run out of the rotating shaft.

Abstract: The friction between vehicle wheels provided with rubber tires follows three influence curves (5, 6, 8). The friction between a wheel with rubber tire and a road surface is represented by a measuring result curve (1-4) the shape of which is determined symptotically from the rubber tire influence curve (6). Thus the measuring result curve (1-4) will have a characteristic shape with maximum values (1A-4A). The maximum friction is determined by the influence curve of the rubber tire and the road surface respectively, also denoted the maximum friction influence curve (8). Each influence curve has its mathematical model. In the mathematical model for the maximum friction influence curve (8) there is incorporated a slip speed, properties of the car tire and road surface-to-car tire properties. The car tire properties and the pavement-to-car tire properties can be determined as process parameters by measurement.

Abstract: A tester of the invention has a horizontal base with a vertical column that supports vertical guides for guiding a carriage that supports a rotary drive mechanism for an upper specimen which is secured in a chuck and engages a lower specimen supported by an interchangeable bowl. The tester is also provided with a computerized measuring system for precisely measuring characteristics to be tested. The main distinguishing feature of the tester of the invention is a that a flexible coupling that may have at least one degree of freedom (preferably three) is installed in a link between a rotary motion unit and the chuck for fixing the upper specimen. In other words, the upper specimen is fixed in a self-aligning manner so that its flat working surface is always maintained in full surface-to-surface contact with the lower specimen.

Abstract: In a stick-slip detection method, the displacement of a movable member having a slidable contact portion is detected. A first quantity of state is calculated on the basis of the detected displacement of the movable member. A second quantity of state, which can be estimated from the first quantity of state, is calculated on the basis of the detected displacement of the movable member. An estimated quantity of state is calculated by estimating a second quantity of state from the calculated first quantity of state by using the relationship between the first and second predetermined quantities of state which are obtained from the displacement of the movable member in a normal sliding state. The calculated second quantity of state is compared with the estimated quantity of state to determine an abnormal sliding operation of the movable member on the basis of the comparison result. A stick-slip detection apparatus is also disclosed.

Abstract: This invention is a compact and portable apparatus directed toward measuring the coefficients of both static and sliding friction or slip resistance occurring between two surfaces. Means are provided for determining and recording data to establish such friction accurately, repeatably, and in a form suitable for computer entry and data processing. Improvement over the prior art is provided with respect to mechanical configuration, ease of use, plus the acquisition and analysis of data, particularly for conditions involving wet or damp surfaces. A method is disclosed for essentially automatic determination of coefficient of friction.

Abstract: An apparatus for measuring the static friction properties of materials. The apparatus has a means for applying shear force to a sled and table interface in a smooth and repeatable manner. The apparatus operates without operator interference in terms of placing a load on the material to be tested. The apparatus contains a shear type load cell which operates at the same location in the apparatus at which the shear force is applied to a contact interface and at which static friction is generated.

Abstract: The invention provides a process for the advance recognition of the hydroplaning of a vehicle tire on a wet road, in which the rotational speed of the wheel carrying the tire is sensed by a rotational speed sensor and the frequency spectrum of the rotational wheel speed is evaluated. According to the invention, in the frequency range above 20 Hz, the natural resonance behavior of the rotational tire vibrations is evaluated continuously, and a conclusion on hydroplaning of the tire is drawn from detuning of the rotatory natural frequencies.

Abstract: A conveyor scale assembly for use in combination with a conveyor belt for weighing an article on the moving conveyor belt. The conveyor scale assembly is comprised of a slider bed which contacts the underside of the moving conveyor belt which generates a friction force between the conveyor belt and the slider bed. Attached to the slider bed is a sensor which continuously measures the friction force and transmits data representing the measured friction force. A CPU receives and processes the representative data and provides a weight for the article on the conveyor belt.

Abstract: Evaluation apparatus for detecting the onset parameters of friction, wear and groan and squeal noise characteristics associated with a specimen of a particular brake friction material composition is provided with a movable apparatus table which carries both a variable-speed electric motor that drives a brake rotor and that has a near-zero speed capability and a reversible electric motor that may be selectively and independently actuated to advance the brake rotor into friction contact with a friction material specimen and with a normal-force that correlates to the output torque of the reversible electric motor.

Abstract: The present invention is related to a method for measuring vehicle motion resistances using the vehicle coast-down testing method. More specifically, the initial coast-down speed of the vehicle is divided into a low speed range and a high speed range. Each range is tested to obtain physically meaningful test variables for each range. By combining the obtained variables, the length of the test road required for previous coast-down test methods can be significantly reduced. Additionally, vehicle motion resistances may be more accurately measured and analyzed.

Abstract: An apparatus and process for monitoring conditions of a control valve including a valve element operated by a drive controlled by a position controller. A spindle extends into a valve chamber through a dynamic seal and connects the valve element to the drive. The condition of the seal is monitored by measuring start-up time, stopping time and distance travelled. The start-up time relates to the time between application of control current to the position controller and sensing movement of the valve element. The stopping time relates to the interval between application of a second control current to the position controller and sensing the valve element has stopped. The distance travelled relates to distance the valve clement travels during the stopping time. A time difference is determined by subtracting the stopping from the starting time and is calibrated to a seal coefficient of friction. The distance travelled is also calibrated to a seal coefficient of friction.