Patent Application
20090259377
The present invention relates to ergonomics, in particular to the ergonomics of a vehicle driver as a biomechanical system. More specifically, the invention relates to a method and system for shortening brake-activation reaction time. In particular, the invention concerns a method and system for finding a position for an under-thigh support that provides the shortest brake-activation reaction time. The aforementioned under-thigh support is intended for use by a vehicle driver for supporting and securing the right leg in the position from which the foot of the driver can be turned from the accelerator pedal to the brake pedal in the shortest possible time. The method and system of the invention makes it possible to adjust the position of the under-thigh support for each person in the driver's seat.
Car crashes now claim more than 40,000 lives each year in the United States, a number that has slowly declined from approximately 50,000 per year over the last four decades. Automobile crashes are the leading cause of death among people between the ages of one to 34 years, accounting for 3.4 million nonfatal injuries annually and costing an estimated $200 billion. Rates of automobile fatalities and injuries per driver and per mile driven have decreased substantially because of safer cars and roads, laws that discourage drunk driving, and other measures; however, the absolute toll of automobile crashes remains high.
By the year 2025 33 million people will be 70 years or older in America. This segment of the population will be growing 2.5 times as fast as the total population. These senior citizens will comprise the largest percentage of “slow reaction” accidents. Slowly but surely senior citizens have developed a higher accident ratio than teenagers. Also, by 2025, the total costs for motor vehicle accidents in the United States will exceed 450 billion dollars.
Heretofore many studies have been conducted to improve the ergonomics of a vehicle seat. For example, “Survey of Auto Seat Design Recommendations for Improved Comfort” by M. P. Reed, et al., (University of Michigan, Transportation Research Institute, Ann Arbor), 1994, contains a review of a large body of literature with emphasis on fit parameters related to anthropometric measurements; feel parameters, including pressure distribution and vapor permeability; and support parameters that are defined with respect to seat posture. Particular attention is given to appropriate lumbar support.
Other studies aimed at measuring the reaction time of a driver in dangerous situations can be found in the following publications and Internet material: (1) “Reaction-Time Measurement and Real-Time Data Acquisition for Neuroscientific Experiments in Virtual Environments” by J. Valvoda, et al, Aachen University (http://www.rz.rwth-aachen.de/global/show_document.asp?id=aaaaaaaaaaaxpci); (2) Reaction Time of Drivers to Road Stimuli, Monash University Human Factors Group, Report HFR-12, by T. Triggs and W. Harris (http://www.monash.edu.au/muarc/reports/Other/hfr12.html); and (3) How the Driver Reaction Meter Works (http://www.sibtec.com/driverhowitworks.html).
U.S. Pat. No. 6,170,355 issued in 2001 to W. Fay, III discloses an easily adjustable foot-operated pedal assembly, such as a brake pedal (for use in heavy equipment) that can be placed in multiple positions to accommodate people of differing heights and body shapes.
The necessity for a raised under-thigh support is mentioned in many advertisements for modern cars. For example, “Nissan 350Z GT—MotorBar Road Test” states “a raised bolster in the middle of the seat cushion helps give extra under-thigh support for more precise operation of the pedal.” In the pamphlet, “Follow-Up Test: 2006 Jeep Grand Cherokee SRT8” states “long-haul comfort is commendable, too, with excellent under-thigh support and feeling of the seats wrapping around.”
Investigations show that the total stopping distance of a vehicle comprises four components: human perception time, human reaction time, vehicle reaction time, and vehicle braking capability.
Human perception time is the time it takes a driver to see a hazard and the brain to realize that it is a hazard requiring immediate reaction. This component of stopping distance can be affected by age, fatigue, and concentration levels of alcohol. Human reaction time is the time it takes to move the foot from the accelerator to the brake pedal and then to depress the pedal when the brain realizes danger. Moving from the accelerator to the brake takes approximately 500 ms (according to the University of Iowa).
Heretofore many studies have been conducted in order to determine the response time for pressing the brake pedal. For example, the article “Response Time” by Charles C. Roberts, Jr. (http://www.croberts.com/respon.htm) describes a test apparatus that evaluates this reaction time. As soon as the light turns red on the console, the driver releases the accelerator and applies the brake, and the reaction time is measured. This form of testing is often called “simple reaction time” because it is the result of a single stimulus: the red light. Reaction times are typically on the order of ¾ of a second. However, response times are more complex and can be as high as 3 to 4 seconds because response time consists of perception/decision time plus reaction time. Perception/decision time is the time it takes to view a hazard and to decide what to do about it. Reaction time is the time it takes to perform a particular function once a decision is made. The response time for removing one's hand from a hot skillet is relatively quick and is on the order of approximately a half second. In this example, the natural response to excessive heat bypasses visual sensors, allowing for a quicker response time. Driving an automobile requires a high degree of visual processing, which tends to extend response times. What can be gleaned from the discussions in the article is that response time is a distributed quantity because of variability in people as well as in situations that require a response. The accident-reconstruction community often assumes a maximum 2.5- to 3.0-second response time. This applies to most accidents involving obvious hazards. Other accidents involving less defined or confusing hazards may result in longer response times. Other factors that extend response time are age, time of day, gender, and chemical usage, suggesting that response time is typically characteristic of a particular set of circumstances encountered in an accident.
There are many other studies of response times and their usage, but none of these studies takes into account the effect of finding the most optimal physical position for the driver's leg relative to the accelerator and brake pedal.
When driving a vehicle, the driver's leg that controls the accelerator and brake pedal can be considered a biomechanical system, the model of which is shown in
Let us consider movements of the driver's leg when one drives a car with an automatic gearbox wherein two pedals, i.e., the accelerator pedal and the brake pedal, are used to control the car. Although in reality these movements are more complicated, in a simplified form they can be considered as the following two modes.
Let us assume that for the initial position of the leg in the first mode, the foot FT is on the accelerator pedal 20. When braking is needed, the driver with relatively short legs first slightly raises the foot FT from the floor F so that the heel disconnects from point H and the leg shifts sidewise to the brake pedal 24. In this movement the entire leg is raised relative to the point PF as a fulcrum. The driver then turns the entire leg relative to the plane I-I to the plane II-II and moves the leg down in order to depress the brake pedal 24.
In the second mode, which is more typical for a driver with relatively long legs, in order to brake from the position on the accelerator pedal 20, the driver merely turns the foot FT relative to the point H.
In reality, the aforementioned movements are more complicated and may comprise a combination of both movements simultaneously. In the context of the present patent application, the movement of the foot from the accelerator pedal to the brake pedal also includes the movement of pushing on the brake pedal until actual initiation of the brakes, i.e., to the moment when the brake lights activate.
It is important to consider the aforementioned movements with regard to the moment of braking. The inventor has been experimentally proven that when a human being accomplishes braking movements on the basis of subconscious reflexes, the aforementioned movements are not at all optional. In other words, there exists a certain unnatural position of the pedal-controlling leg that can provide a more optimal braking condition, i.e., the condition that allows shortening of the braking time and hence of the braking path.
To provide the most optimal position of a driver's right leg in order to shorten the momentum for movement of the feet from the accelerator pedal to the brake pedal and to subsequently depress the brake pedal, the inventor herein has developed a special under-thigh pillow that can be used for supporting and fixing the driver's right leg in the aforementioned optimal position. This under-thigh pillow is the subject of U.S. Pat. No. 7,255,396 issued in 2007 to the same applicant (Sergey Anikin) and is titled “Ergonomic thigh support and method of uniformly distributing pressure on the thigh surface of a seated person”, which is incorporated herein by reference.
Use of the aforementioned under-thigh support is justified only if the aforementioned under-thigh support is installed and fixed in a predetermined position that depends on specific anthropometric data of each individual driver. In other words, the most optimal position of the under-thigh support of the aforementioned patent application will differ for people of various builds.
In order to determine the shortest time needed for a driver to switch the foot from the accelerator pedal to the brake pedal and to push on the brake pedal in an emergency, the inventor herein has developed a system that is disclosed in pending U.S. patent application Ser. No. 11/515,192 filed on May 9, 2006. According to this system, when a danger-imitating signal lamp activates, preferably at random, a first photo-receiver receives the light signal of the lamp and sends it to a signal amplifier, wherefrom the amplified signal is sent to a computer by the time counter. The computer begins to register the length of the light signal. As soon as the driver reacts to the light signal of the signal lamp, he or she moves his or her foot from the accelerator pedal to the brake pedal and pushes on the brake pedal, thus igniting the brake lights. The light of the brake-signal lamp is also activated and sent to the computer. The time interval between the moment of initiation of the first photo-receiver and initiation of the second photo-receiver corresponds to the time of the driver's response to the light signal, which imitates a danger plus the time of transfer from the accelerator pedal to the brake pedal. The above-described test is repeated several times at different positions of the under-thigh support to find the position most optimal for the shortest braking time.
Although such a system, in principle, operates reliably and accomplishes its function properly, one of the disadvantages of the system is that it measures only the integral time from initiation of the danger-imitation light signal to the moment of activation of the brake signal lamp located on the rear side of the vehicle. In other words, there is no information about mental reaction time of the driver from the danger signal to the beginning of transferring one's foot from the gas pedal to the brake pedal, time of transfer of the foot from the gas pedal to the brake pedal, and time of braking from initiation of pressure on the brake pedal to the complete stop of the vehicle. Another disadvantage of the known system is that a part of the system components, i.e., photo-receivers, etc., are located on the outer side of the vehicle. This limits or hinders use of the brake-time control system, e.g., during rain or the like, and requires mounting of the photo-receivers to the vehicle body and dismantling them after the test is completed.
It is an object of the invention to provide a system for finding the shortest brake-activation time with use of an optimally positioned driver's seat and/or an under-thigh support, wherein the system as a whole is located inside the vehicle in a driver's compartment without any components on the outer side of the vehicle. It is another object to provide the aforementioned system wherein the brake signal lamp is not involved in measuring brake-activation time. It is a further object of the invention to divide the integral brake-activation time into intervals corresponding to mental reaction time of the driver from the danger signal to the beginning of foot transfer from the gas pedal to the brake pedal, time of transfer of the foot from the gas pedal to the brake pedal, and time of braking from initiation of pressure on the brake pedal to complete stop of the vehicle. It is a further object to provide a method for finding the optimal position of a driver's seat and/or an under-thigh support for shortening brake-activation time.
The system of the invention for finding the shortest brake-activation time with the use of an optimally positioned driver's seat and/or under-thigh support consists of a pair of tilt sensors, i.e., sensors that react on deviation of an object from the real vertical or horizontal position, that are attached to a gas (accelerator) pedal and a brake pedal of a vehicle, respectively. Both tilt sensors are connected to a multichannel A/D converter that converts analog voltage signals of the sensors into respective digital signals, which are sent to a computer, e.g., through USB connectors. The system is also provided with a danger-signal lamp and a photo-receiver that reacts on the light signal of the aforementioned lamp. Both the signal lamp and the photo-receiver may be located outside or inside the vehicle. The remaining components of the system are all located inside the vehicle. The computer initiates the danger-imitation light signals at random. All sensors and the danger signal generation lamp are connected to a power supply unit. In order to nullify the initial positions of the tilt sensors, they are adjusted to the horizontal position prior to testing. The sensors may be installed in U-shaped holders that can be fit onto the neck of the pedal rod or any other part that is rigidly connected to the pedal and attached thereto in a position not interfering with normal operation of the accelerator and brake pedals. The principle of operation of the system consists of the following. First, an under-thigh support of the type disclosed, e.g., in U.S. Pat. No. 7,255,396, is placed under the right thigh of a driver sitting in the driver's seat of a vehicle that is controlled by the system. The system components, i.e., sensors, photo-receiver, computer, danger-imitating lamp, etc., are activated when connected to the power supply. In the normal state, the danger-signal imitating lamp is not lit.
Although the test vehicle is stationary, it is assumed that at the beginning of the test, the driver depresses the accelerator pedal with the right foot as though he or she were driving the vehicle under normal conditions. When the danger-signal imitating lamp is lit by a signal randomly generated by the random-number selection function of the computer or from a separately installed conventional random-number generator, the driver is assumed to be confronted with an unexpected obstacle or a dangerous situation that requires emergency braking. The moment at which the danger-imitating signal is activated is registered on the computer.
It is understood that some time is required for the driver to perceive a danger signal and that this danger-signal perception time may depend on factors such as driver fatigue, the driver's vision, the driver's reaction-response time which in turn depends on the driver's age, experience, etc. When the driver reacts to the danger signal, he/she releases the accelerator pedal and transfers the right foot from the accelerator pedal to the brake pedal (we are considering here a situation involving an automatic gearbox, i.e., not a stick-shift-controlled gear box, although the principle of the invention applies to the non-automatic gearbox as well). The computer registers the moment at which the foot transfers from the accelerator to the brake pedal, and the end of this time period is fixed when the tilt sensor connected to the brake pedal begins to change its angular position. The next period of time recorded by the system is that from beginning of braking, e.g., from initiation of tilt-sensor position change to the end of the brake period, i.e., to full stop of the brake pedal.
Upon completion of the first test, the driver marks the position of the under-thigh support, and the test is repeated one or more times with the same measurements but with different positions of the thigh support. The measurement results are compared, and the under-thigh support is fixed in the position that corresponds to the shortest time interval between the light signal and ignition of the brake light. Time signals measured in the same positions of the driver but without the use of the under-thigh support appeared to be longer. This showed that the use of the under-thigh support developed by the application and disclosed in the previous U.S. patent is an efficient means for shortening brake-activation time on the basis of ergonomic factors and characteristics of each specific driver. Moreover, division of integral brake-activation time into separate time intervals allows for control and analysis of various periods of braking time. What is important is that the system and method of the invention apply to optimization of the position not only of the under-thigh support but also to the position of the seat relative to the control elements (pedals, levers, etc.) of the vehicle, as well as for comparing and testing the designs of various seats from the ergonomic point of view.
The system of the invention for finding the shortest brake-activation time will now be described in more detail with reference to the accompanying drawings, wherein
The system of the invention for finding the shortest brake-activation time, which as a whole is designated by reference numeral 20, contains a pair of tilt sensors 22 and 24, i.e., sensors that react on deviation of an object from the real vertical or horizontal position and constitute main components of the system 20. Such sensors are described, e.g., by D. Pheifer and W. Powell in “The Electrolytic Tilt Sensor” (http://www.sensorsmag.com/articles/0500/120/main.shtml). Electrolytic tilt sensors are capable of producing extremely accurate pitch and roll measurements in a variety of applications. They provide excellent repeatability, stability, and accuracy when operating at low frequencies, and are available in a variety of packages with varying tilt range and resolution. These rugged, passive devices can be used in environments of extreme temperature, humidity, and shock.
The sensor is filled with an electroconductive liquid. As the sensor tilts, the surface of the fluid remains level due to gravity. Conductivity between the two electrodes of the sensor is proportional to the length of the electrode immersed in fluid. Electrically, the sensor is similar to a potentiometer, with resistance changing in proportion to tilt angle.
To prevent electrolysis, alternating current must be used to excite the sensor. The required frequency and symmetry of the AC waveform depend on the chemistry of the fluid and composition of the electrodes. The frequency must be high enough so that the process described above is reversible. For some electrolytes this frequency can be from 1000 Hz to 4000 Hz.
As shown in
The USB-1616FS has an all-aluminum chassis that ensures a device rugged enough for any application. The combination of the USB-1616FS and Measurement Computing's DAQ software suite provides a complete and easy data acquisition solution.
The system is also provided with a danger-imitation-signal means, e.g., signal lamp 34 and a danger-signal perception sensor, e.g., a photoreceiver 36 that reacts on the light signal of the aforementioned lamp 36 (
In order to nullify the initial positions of the tilt sensors 22 and 24, they are adjusted to the horizontal position prior to testing. As shown in
The principle of operation of the system consists of the following. When an under-thigh support (not shown) is used, first this under-thigh support, e.g., of the type disclosed, e.g., in U.S. Pat. No. 7,255,396, is placed under the right thigh of a driver sitting in the driver's seat of a vehicle 30 controlled by the system 20 (
Although the test vehicle is stationary, it is assumed that at the beginning of the test, the driver depresses the accelerator pedal 26 with the right foot as though he or she were driving the vehicle 30 under normal conditions. When the danger-signal imitating lamp 34 is lit by a signal randomly generated by the random-number selection function of the computer 30 or from a separately installed conventional random-number generator 30a, which is conventionally shown in the drawing by dash-and-dot lines, it is assumed that the driver is confronting an unexpected obstacle or a dangerous situation on the road that requires emergency braking. The moment of generation of the danger-imitating signal is registered on the computer 30.
It is understood that some time is required for the driver to perceive a danger signal and that this danger-signal perception time may depend on factors such as driver fatigue, vision of the driver, reaction-response time of the driver which in turn depends on the driver's age, experience, etc. When the driver reacts to a danger signal, he/she releases the accelerator pedal 26 and transfers the right foot from the accelerator pedal 26 to the brake pedal 28 (we are considering here an automatic gearbox, i.e., not a stick-shift-controlled gear box, although the principle of the invention is applicable to the non-automatic gearbox as well). The computer 30 registers the moment at which the foot transfers from the accelerator pedal 26 to the brake pedal 28, and the end of this time period is fixed when the tilt sensor 24 connected to the brake pedal 28 begins to change its angular position. The next time period recorded by the system 20 is the time from the beginning of braking, e.g., from initiation of change in the position of the tilt sensor 24 to the end of the brake period, i.e., to the full stop of the brake pedal 28.
Upon completion of the first test, the driver marks the position of the under-thigh support 41, and the test is repeated one or more times with the same measurements but with different positions of the thigh support 41. The results of measurements are compared, and the under-thigh support 41 is fixed in the position that corresponds to the shortest time interval between the light signal and ignition of the brake light. Time signals measured in the same positions of the driver but without use of the under-thigh support appeared to be longer. This showed that the use of the under-thigh support 41 developed by the application and disclosed in the previous U.S. patent is an efficient means for shortening brake-activation time on the basis of ergonomic factors and characteristics of each specific driver. Moreover, division of integral brake-activation time into separate time intervals allows for control and analysis of various periods of braking time. What is important is that the system and method of the invention makes it possible to optimize the position not only of the under-thigh support 41 but also of the car seat 39 relative to the control elements (pedals 26 and 28, lever 44 (
An example of the records by device 20 is illustrated on the screen of the laptop 30 shown in
After the accelerator pedal is completely released, which corresponds to the end of period t2, the driver transfers the right foot from the accelerator pedal 26 to the brake pedal 28. This time interval is t3. The bar graph 54 with time t4 corresponds to depression of the brake pedal 28. The braking period is stopped at the end of time interval t4, which corresponds to completion of the brake-pedal stroke.
Thus, it can be seen that the method and system 20 of the invention make it possible to divide the total braking time T into the aforementioned separate specific periods t1, t2, t3, and t4, which in addition to finding the shortest total braking time T allows evaluation of factors such as effect of driver fatigue, reactive capacity of the driver to emergency situations, the most ergonomic position of the leg and foot, etc. Furthermore, the method and system 20 of the invention make it possible to analyze the effect of the position of the car seat and/or a thigh support on the aforementioned time periods T, t1, t2, t3, and t4.
It is shown that the invention provides a system and method for finding the shortest brake-activation time with the use of an optimally positioned driver's seat or/and under-thigh support, wherein the system as a whole is located inside the vehicle in the driver's compartment without any components on the outer side of the vehicle. In the system of the invention, the brake-signal lamp is not involved in measurement of brake-activation time. Integral brake-activation time is divided into intervals corresponding to mental reaction times of the driver from the danger signal to the moment at which the foot transfers from the gas pedal to the brake pedal, the moment at which the foot transfers from the gas pedal to the brake pedal, and the braking time from initiation of pressure on the brake pedal to the complete stop of the vehicle.
Although the invention has been shown and described with reference to specific embodiments, it is understood that these embodiments should not be construed as limiting the areas of application of the invention and that any changes and modifications are possible provided that these changes and modifications do not depart from the scope of the attached patent claims. For example, the danger-imitation signal may be in the form of a sound signal, the combination of a visible and a sound signal in the form of an object that unexpectedly appears in front of the windshield, etc. It is not necessary to switch off the danger-signal lamp, and this lamp may remain ignited to the end of the test cycle. The signals can be wirelessly transferred from the sensors to the computer located outside the vehicle. The principle of the invention also applies to vehicles in which the driver sits on the left.
The present patent application relates to pending U.S. patent application Ser. No. 11/5115,192 filed by Sergey Anikin on May 9, 2006 and is titled “Method and System for Shortening Brake-Activation-Reaction Time.”
