Elevator algorithm

Abstract: An elevator self-diagnostic system monitors the operative status of various elevator components and upon sensing an error initiates action to bring the elevator car to a safe operating state. The system then logs the error. The diagnostic system then analyzes the error and the conditions prevailing at the time the error occurred and, if necessary, a corrective action is then taken to resolve the error. This allows the elevator system to be brought back into service more quickly than would otherwise be possible. Specifically, a number of tests are serially performed on various elevator components, such as the motor drive, the position sensors, etc. When an error, or fault, arises in a system component, a selt-diagnostic system logs a preselected error level which has been assigned to the particular fault. A preselected action is then taken according to the particular error. For example, if the output of the position encoder is lost while the elevator car is running, then the elevator car's velocity is decreased at a constant rate until the car is brought to a stop. A short time later, the car is restarted and proceeds toward its target floor.

Abstract: A queuing architecture and method for scheduling disk drive access requests in a video server. The queuing architecture employs at least two access request queues for each disk drive within a disk drive array, and a queue selector for selecting the first and second queues. The first queue is for disk access requests by steady-state users requesting new data streams who are currently viewing a program from the video server. The second queue is for all other types of disk access requests, including requests by new users, requests for loading content, disk maintenance, meta-data synchronizing, and the like. Steady-state disk access requests are serviced in order of ascending time deadlines. The queue selector gives highest priority to requests in the first queue, and requests from the second queue are serviced only upon a guarantee that all of the steady-state requests in the first queue will meet their time deadlines in the worst case access times for the disk drives. The second queue may comprise multiple queues to provide a queuing hierarchy including a third queue. Non-steady-state disk access requests are serviced on a first-in-first-out basis. The queue selector establishes priority in response to the location of the data upon a disk in a disk drive, and data may be stored in a disk drive based upon the queuing priority. The selecting and forwarding of the access requests to a disk drive may be performed repeatedly while an internet queue within a disk drive is not full, and there are outstanding access requests for that disk drive.

Abstract: A procedure for scheduling multiple process requests for read/write access to a disk memory device within a computer system. The procedure considers disk characteristics, such as the number of sectors per track, the number of tracks per cylinder, speed of disk rotation and disk controller queuing capability in determining the optimal order for executing process requests. Process requests are placed in packets within an execution queue, each packet including up to a predetermined maximum number of requests. Within the packets, the process requests are sorted in ascending/descending order by the cylinder number to which the requests desire access, while within each cylinder the requests are placed in next-closest-in-time sequence.

Abstract: A disk scheduling system with bounded request reordering. Disk access requests may be performed during traversals of a disk head across a disk. Each traversal may have a specified direction of motion. A plurality of disk accesses may be performed during a disk head traversal. The overall number of disk access requests for a given disk head traversal may be limited to a maximum number N. By limiting the number of disk requests for each traversal, a bound may effectively be placed on the amount of time it takes to satisfy any single disk request.