Walking Distance Measurement Systems

POSIFA Microsystems developed walking distance measurement systems as shown above. These systems can measure the distance for many walking ways to take including:

• Walk with your spouse, child, or friend
• Walk the dog
• Use the stairs instead of the elevator
• Park farther from the store
• Better yet, walk to the store
• Get up to change the channel
• Window shop
• Plan a walking meeting
• Walk over to visit a neighbor
• Walk around the garden or do a little weeding 

There are countless physical activities out there, but walking is a good form of exercise for many people. Knowing walking distance will help people develop an exercise program that's effective for losing weight, increasing aerobic fitness, and improving heart health.

Many efforts have been made to measure the distance traveled by humans for a long time. There are several ways to measure the distance moved by walking or running in daily life, some of which already use commercial products, but none of them is ideal and perfect.

As well know, one way is based on radio frequency, such as GPS, or may use optical-based systems, such as video tracking. Such systems are not available indoors and degrade significantly in deep city canyons.

As an alternative, the measurement can be made by self-contained tracking systems. Such systems use commercially available MEMS inertial sensors and magnetic sensors. However, the performance of MEMS accelerometers and angular rate sensors is limited by random noise and calibration error. When they are used in a position tracking systems, it becomes the source of unbounded growth in position error.

A new walking distance measurement system is developed by POSUFA Microsystems, which is based on their MEMS thermal flow sensors. Human walking exhibits variability from step to step. As above listed walking ways, all most each step may be different in walking direction or in step length. It is impossible to do correct and precise measurement using available distance measurement systems. Only the POSIFA systems can do that because it measures the distance simply by adding all step length together. 

Each human walking step consists of stance phase, swing phase, and stance phase again. In any stance phases the foot traveling velocity is zero. In the swing phase the foot traveling velocity increases from zero to maximum and then decreases from maximum to zero like a pendulum curve. The thermal flow sensor can be managed to measure any instantaneous velocity of a particular foot traveling step. Then the instantaneous velocity is integrated over the traveling time of the particular step to produce the length of the particular step. All the lengths of each traveling steps can be accumulated to provide the distance of this human walking event.

In such systems, the thermal flow sensor only measures the instantaneous velocity.  The measurement signals are sent to a smart phone using Wi-Fi communication. The Smart phones are useful in this application because they are portable and have sufficient computational power to compute and analyze the measurement signals to provide the walking distance and other information people are interested. 

Thermal Flow Sensors for Man-Potable Vehicles Applications

Thermal Flow Sensors for Man-Potable Vehicles Applications

Man-portable air vehicles (UAVs) or micro air vehicles (MAVs) can be used in

many dangerous civil and military missions without any risk to human life, and they also have many potential industrial applications such as plant supervision, power line and construction site inspection, pollution and weather monitoring, forest fire and disaster control, etc.

All these vehicles operate exclusively within the atmospheric boundary layer,

which typically extends up to 5 km above ground level depending on surface heating, climatic conditions, and terrain. The flow in the atmospheric boundary layer is dominated by horizontal transport of atmospheric properties. As air travels over buildings and various obstacles, there will be a local increase in wind speed. It has been shown that mean wind speeds above a certain threshold can make the air speed vary substantially. When a steady 4.6 m/s magnitude wind is presented it is inability of an MAV to reach its pre-programmed waypoints. This degradation in performance puts the aircraft at risk and often leaves the MAV unable to complete its mission.

In order to improve the performance of the air vehicles a powerful onboard

sensing system is required. This sensing system can detect individual air speeds in a turbulent boundary layer. Once detected, the turbulent influence can be suppressed or eliminated by an action of micro electromechanical devices.

As shown in figure 1, POSIFA thermal flow sensors are ideal for the onboard

sensing system. These thermal flow sensors have the benefits of miniature size, low power dissipation and fast response time, which is essential for detecting turbulent flow. The miniature size allows for their installation in small spaces without significantly interfering with the flow and consequently altering its behaviour.                   

These thermal flow sensors can be used for detecting the surface velocity

distribution over critical locations of the wing area, such as the points of flow transition, reversal, or separation.

POSIFA thermal flow sensors can be used to determine three flight parameters: air

speed, angle of attack and angle of sideslip. As shown in figure 2, so as to do so an array of thermal flow sensors is installed over critical locations of the wing area, such as the points of flow transition, reversal, or separation. The signal of each thermal flow sensor is send to a microcontroller through wireless communication. The microcontroller will act the micro electromechanical device for suppressing or eliminating the turbulent influence.

 Figure 1. An assembled printed circuit board with a POSIFA thermal flow sensor and a lot of diced POSIFA thermal flow sensor chips surrounding the PCB.

These thermal flow sensors can be used for detecting the surface velocity

distribution over critical locations of the wing area, such as the points of flow transition, reversal, or separation.

POSIFA thermal flow sensors can be used to determine three flight parameters: air

speed, angle of attack and angle of sideslip. As shown in figure 2, in order to do so an array of thermal flow sensors is installed over critical locations of the wing area, such as the points of flow transition, reversal, or separation. The signal of each thermal flow sensor is send to a microcontroller through wireless communication. The microcontroller will act the micro electromechanical device for suppressing or eliminating the turbulent influence.

Figure 2. An Unmanned air vehicle equipped with a POSIFA thermal flow sensor array controlled by a microcontroller.

MEMS Pirani Sensors for Plasma Sterilization Applications

Low pressure plasma sterilization has been developed as secure sterilization

methods and has already been put to practical use for medical equipment. Although the mechanisms are not yet fully understood, the following cellular inactivation mechanism has been reported: ultraviolet radiation in the far-ultraviolet and mid-ultraviolet range is capable of damaging nucleic acids (DNA, RNA) and proteins.

In order to produce such ultraviolet radiation the pressure of the gas mixture used

as plasma source should be well controlled in the range of 13 to 130 Pa.

We have developed Pirani sensors which can be used to control the pressure of

the gas mixture. The amplified response of a Pirani sensor to pressure variation is shown in the following figure. It can be seen from the figure that the controlled pressure locates the sensitive range of the Pirani sensor.

Medical Liquid Thermal Flow Sensors

Recently, our thermal flow sensors have been developed

for medical liquid applications. These new applications require low noise, high reproducibility, short response time, battery powered, potable and wearable, and low-cost disposable. Our sensors meet all these requirements because they are fabricated using a CMOS comparable technology and are based on a structure integrating a heater and a thermopile in a single chip.

   The following figure shows a typical characteristic line of 1% NaCl in DI water (stroke-physiological saline solution) flow measured by a liquid thermal flow sensor.

Disposable Water Flow Sensors

    POSIFA Microsystems now provide disposable water thermal flow sensors with outstanding performance.  

     Medical instrumentation has recently been moved outside the hospital and clinic into the home to help keep health care costs down whilst providing a better level of care. Sensors are an important part of the new technology for allowing this to happen.

     At the present, POSIFA’s thermal flow sensors are mainly used for air flow determination in human respiration. However an increasing demand is observed for liquid measurements in smallest flow ranges for medical applications. 

     Compared with traditional flow sensors, the thermal flow sensors have the advantages of highly precise measurement and high repeatability, short response time, low power consumption, smallest dimensions, adhesive-free packaging and low-cost. 

     On the market there are only micro pump systems available that work in a controlled but not in a regulated mode. This means that an extrinsic disturbance will lead to a falsification of the flow rate. It is not feasible that those systems run under disturbance free conditions. Therefore for small, cheap and especially regulated measurement our thermal flow sensor is a satisfying solution.

A Perfume Bottle with a Silicon Based MEMS Vaporizer

     As the vaporizers developed by POSIFA can be combined to comprise a total olfactory system, a variety of olfactory displays can be realized. Compared with several types of developed olfactory display, our system is much light and small. Since the developed olfactory display comprises of mass flow controllers, inkjet devices, solenoid valves, and fans, it is inevitable to form a larger instrument.  Our system is portable and wearable it can be shaped like a portable perfume bottle.

Non-invasive blood glucose monitor 

    A micro-optical-mechanical-electro-system (MOMES)-based non-invasive blood glucose monitor comprises a micromachined infrared optical filter array, a micromachined infrared mechanical modulator array, at least one micromachined infrared tunable filter, and at least one infrared detector. Each optical filter is aligned with a mechanical modulator along its optical axis direction. The optical filter continuously divides a monochromatic infrared light in a wavelength range within 0.8 to 25 micron from an infrared light. The aligned mechanical modulator turns the monochromatic infrared light into an alternating monochromatic infrared light. The tunable filter is aligned with the infrared detector along its optical axis direction. The tunable filter selects the back-diffused alternating monochromatic infrared light emitted from a measured blood subject that is illuminated by the alternating monochromatic infrared light. The infrared detector converts the back-diffused alternating monochromatic infrared light into an alternating electronic signal. Then a photo-integrated circuit (IC) combines with the infrared detector for synchronous detection and amplification of the electronic signal generated by the synchronous detection.

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