Browse Prior Art Database

Control Malfunction Detection

IP.com Disclosure Number: IPCOM000084961D
Original Publication Date: 1976-Feb-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 3 page(s) / 65K

Publishing Venue

IBM

Related People

Buhler, OR: AUTHOR [+2]

Abstract

The circuits as depicted in the drawings determine both range and rate malfunction of a device.

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Control Malfunction Detection

The circuits as depicted in the drawings determine both range and rate malfunction of a device.

In Fig. 1, controller 10 drives power amplifier 12 which in turn drives motor
14. In several applications, if a malfunction occurs in controller 10 the malfunction detector must be able to detect and isolate the malfunction.

Generally, the output from controller 10 is restricted to operate in a given range (-V to +V). If the drive signal from controller 10 exceeds the restricted range the controller is defective. This defect is referred to as range defect.

In order to measure range defects, the output of controller 10 is fed into range threshold detect circuit 16. Range detect circuit 16 has a positive output and a negative output. In operation, range threshold detect circuit 16 is set at a negative and a positive threshold level. Whenever the signal from controller 10 exceeds either the positive or the negative threshold OR circuit 18 conducts which in turn sets latch 20, thereby indicating that a malfunction occurred.

In addition to the range defect, controller 10 may suffer from a rate defect (i.e., dv/dt is too high). A rate malfunction will cause excessive current to flow in motor 14. In order to sense rate malfunction, the output of controller 10 is fed into rate circuit 22.

Rate circuit 22 determines the rate (i.e., dv/dt) at which the output signal from controller 10 is changing and feeds the rate changing into range threshold detect circuit 24. Range threshold detect circuit 24 is analogous to the range threshold detect circuit
16. The output (positive or negative) of range threshold detect circuit 24 is fed into OR circuit 26, the output of which is used to set latch 20.

Fig. 2 is an actual implementation of a control malfunction detector. M1 through M4 are comparators. The comparator's outputs are open collectors referenced to a -V supply. The open collector outputs allow a DOT OR which may then be level shifted to t...