Optimistic data retrieval in a process control environment
Processing raw data stored in an historian device for determining an amount of products passed through a process element in a process control environment is described. A count value is incremented by a counter at a rate at which products pass through the process element. The count value rolls over to zero when the count value reaches a rollover value R. An historian device periodically receives count value data points from the counter. A deadband value D is set in the historian device for distinguishing between rollovers, resets, and reversals. A client device queries the historian device for an amount of products passed through the process element for a timeframe. The historian device selects a set of count value data points from within the queried timeframe. The historian device determines, based on the selected data points and their quality, an amount of products passed through the process element.
1. A method of retrieving data from an historian device in a process control environment comprising:
receiving in the historian device, a query for a result over a timeframe by an historian device from a client device connected to the historian device;
selecting by the historian device, data points within the timeframe;
identifying in the historian device, data points as having a ‘GOOD’ quality, a ‘BAD’ quality, or a ‘DOUBTFUL’ quality;
setting in the historian device, an ‘OPTIMISTIC’ quality rule mode wherein the historian device includes in the retrieval calculations data points with both a ‘GOOD’ quality and a ‘DOUBTFUL’ quality except that ‘BAD’ quality data points will not be included in a calculation;
wherein the determined amount of products by the historian device is based on the included data points; and
wherein the historian device returns the determined amount of products to the client device.
2. The method of claim 1 wherein at least one of the following:
if a “BAD” quality data point is encountered, then a last known ‘GOOD’ quality data point or a last known ‘DOUBTFUL’ quality data point is used as if the “BAD” quality data point never occurred;
if a “BAD” quality data point is encountered, then a last known ‘GOOD’ quality data point or a last known ‘DOUBTFUL’ quality data point is used as if the “BAD” quality data point never occurred; wherein if a particular data point is a “BAD” quality data point and if there are no points prior to the start of the query, then 0.0 will be used as a starting base value for the particular “BAD” quality data point; and
if a “BAD” quality data point is encountered, then a last known ‘GOOD’ quality data point or a last known ‘DOUBTFUL’ quality data point is used as if the “BAD” quality data point never occurred; wherein if a particular data point is a “BAD” quality data point and if there are no points prior to the start of the query, then 0.0 will be used as a starting base value for the particular “BAD” quality data point, and then the value change for the cycle is calculated from the first actual data point in the cycle, rather than 0.0.
3. The method of claim 2 further comprising:
incrementing by a counter, a count value at a rate at which products pass through the process element;
rolling over the count value to zero by the counter when the count value reaches a rollover value R after which the counter rolls the count value over to 0 and continues incrementing;
receiving by the historian device connected to the counter, count value data points periodically;
setting, in the historian device, a deadband value D for distinguishing among rollovers, resets, and/or reversals;
querying by the client device from the historian device, an amount of products passed through the process element for a timeframe;
selecting by the historian device, a set of count value data points received within the queried timeframe; and
determining by the historian device, based on the selected data points, an amount of products passed through the process element.
4. The method of claim 3 wherein the determining comprises:
determining a reset has occurred if a first data point is greater than a following data point and the first data point is less than R*(1−D/100) and the following data point is less than R*D/100, and determining the amount of products passed through the process element based on the determined reset;
determining a reversal has occurred if the first data point is greater than the following data point and the difference between the first data point and the following data point is less than R*D/100, and determining the amount of products passed through the process element based on the determined reversal; and
determining a rollover has occurred if the first data point is greater than the following data point and it has not been determined that reset has occurred between the first and following data points and it has not been determined that a reversal has occurred between the first and following data points, and determining the amount of products passed through the process element based on the determined rollover.
5. A historian memory storage device and a historian processor including a counter, said historian memory storage device storing statistical data and storing processor-executable instructions for execution by the historian processor for implementing a historian connection module and a historian server module, said processor-executable instructions configured for, when executed by the historian processor:
receiving in the historian device, a query for a result over a timeframe by an historian device from a client device connected to the historian device;
selecting by the historian device, data points within the timeframe;
identifying in the historian device, data points as having a ‘GOOD’ quality, a ‘BAD’ quality, or a ‘DOUBTFUL’ quality;
setting, in the historian device, an ‘OPTIMISTIC’ quality rule mode wherein the historian device includes in the retrieval calculations data points with both a ‘GOOD’ quality and a ‘DOUBTFUL’ quality except that ‘BAD’ quality data points will not be included in a calculation;
wherein the determined amount of products by the historian device is based on the included data points; and
wherein the historian device returns the determined amount of products to the client device.
6. The device of claim 5 wherein the determining processor-executable instructions are configured for at least one of the following:
if a “BAD” quality data point is encountered, then a last known ‘GOOD’ quality data point or a last known ‘DOUBTFUL’ quality data point is used as if the “BAD” quality data point never occurred;
if a “BAD” quality data point is encountered, then a last known ‘GOOD’ quality data point or a last known ‘DOUBTFUL’ quality data point is used as if the “BAD” quality data point never occurred; wherein if a particular data point is a “BAD” quality data point and if there are no points prior to the start of the query, then 0.0 will be used as a starting base value for the particular “BAD” quality data point; and
if a “BAD” quality data point is encountered, then a last known ‘GOOD’ quality data point or a last known ‘DOUBTFUL’ quality data point is used as if the “BAD” quality data point never occurred; wherein if a particular data point is a “BAD” quality data point and if there are no points prior to the start of the query, then 0.0 will be used as a starting base value for the particular “BAD” quality data point, and then the value change for the cycle is calculated from the first actual data point in the cycle, rather than 0.0.
7. The device of claim 6 wherein the determining processor-executable instructions are configured for:
incrementing by a counter, a count value at a rate at which products pass through the process element;
rolling over the count value to zero by the counter when the count value reaches a rollover value Rafter which the counter rolls the count value over to 0 and continues incrementing;
receiving by the historian device connected to the counter, count value data points periodically;
setting, in the historian device, a deadband value D for distinguishing among rollovers, resets, and/or reversals;
querying by the client device from the historian device, an amount of products passed through the process element for a timeframe;
selecting by the historian device, a set of count value data points received within the queried timeframe; and
determining by the historian device, based on the selected data points, an amount of products passed through the process element.
8. The device of claim 7 wherein the determining processor-executable instructions are configured for:
determining a reset has occurred if a first data point is greater than a following data point and the first data point is less than R*(1−D/100) and the following data point is less than R*D/100, and determining the amount of products passed through the process element based on the determined reset;
determining a reversal has occurred if the first data point is greater than the following data point and the difference between the first data point and the following data point is less than R*D/100, and determining the amount of products passed through the process element based on the determined reversal; and
determining a rollover has occurred if the first data point is greater than the following data point and it has not been determined that reset has occurred between the first and following data points and it has not been determined that a reversal has occurred between the first and following data points, and determining the amount of products passed through the process element based on the determined rollover.