Accurate and reliable position information related to rotating objects is desirable for many applications. For example, engine position information can be important to operate an engine with low emissions and high efficiency. In particular, by knowing an accurate engine position, it is possible to precisely time fuel injection and spark as well as provide proper emissions monitoring through high level functions such as misfire detection by instantaneous speed misfire methods. Therefore, it is desirable to assure that a position sensing system has sufficient operating margin to provide proper position information over potential operating conditions including vibration, temperature and high rotational speeds.
One sensing technology used for determination of engine position is with a variable reluctance transducer. Variable reluctance engine position sensors output a sinusoidal signal that has an amplitude and frequency that are proportional to the speed of the rotating object (e.g., an engine flywheel) relative to the position sensor. However, the output of a variable reluctance sensor can be affected by many variables including the proximity of the sensor to the moving object, the magnetic circuit in the sensor, and the properties of the sensed target. The most significant factor other than speed is the sensor distance to the target, normally referred to as air-gap. A variable reluctance system is easy to check for proper build quality as the sensor voltage can be measured during normal engine functional testing. For example, a voltage acceptance criterion can be applied and used to statistically track the quality performance of the engine sensing system. Using this method it is possible to provide voltage threshold limits that can be used to detect errors in the build quality such as a sensor that is not fully installed or a rotating target that is damaged.
Variable reluctance technologies are quickly being replaced by more advanced sensor technologies. One reason variable reluctance technology are being replaced is because they require more complex input circuits in the interfacing module, usually an engine or powertrain control module. Additionally, variable reluctance sensors have required more significant characterization and calibration effort to assure proper lifetime performance.
On the other hand, Hall Effect and giant magneto resistive (GMR) sensors are becoming the typically applied technologies. Hall and GMR sensors provide a simpler output signal which allows for a less complex input circuit in the control module as well as a reduced amount of characterization and calibration effort. Due to the simplified sensor output characteristics, the detection of sensor system degradation at the manufacturing location of the engine is not as robust as for other types of sensors. The sensor signal provides a way to detect if the sensor is functioning at the specific conditions tested but variable data is not available to ensure that the sensing system has sufficient margin for a range of operating characteristics.
In all of these sensors, the primary principle of sensing is to sense a changing magnetic field around the sensing element that is caused by the rotation of the metallic target in front of the sensor. In the variable reluctance sensors, as noted above, this magnetic variability can be directly measured on the finished engine assembly. In the case of the Hall Effect and GMR technologies, it is desirable to obtain the magnetic profile information on the finished engine assembly. Toward this end, the inventor has proposed a method for the measurement of the speed sensor magnetic profile.
The inventor herein has recognized the above-mentioned issues with advanced sensor technologies and has developed a method for determining data associated with quality of a magnetic sensor profile. In one embodiment, present description includes a method for assessing operation of position sensor, comprising: during rotation of an object sensed by a position sensor, storing data associated with quality of a magnetic sensor profile within the position sensor, and outputting position data via a pin of the position sensor; and during non-rotation of the object, outputting at least a portion of the data associated with quality of the magnetic sensor profile via the pin.
By storing data associated with quality of a magnetic sensor profile within a position sensor it may be possible to better assess operation of an advanced position sensor that outputs a modified object position. Further, a sensor that has the capability to output internally measured parameters and diagnostic codes that can reduce the time to diagnose a degraded sensor. Further still, a sensor that outputs two different types of information during two different operating modes through a single output can reduce wiring costs and system complexity.
The present description may provide several advantages. For example, the approach provides for gathering and reporting quality of a magnetic sensor profile that is not otherwise available. Further, the signal quality data may include information related to each tooth of the sensed object so that signal degradation can be isolated to specific sensor system elements. Further still, the approach allows sensor system operation to be verified after manufacturing.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.