Positive feedback control

The parameters used in the program give a steady-state solution, representing, however, a non-stable operating point at which the reactor tends to produce natural, sustained oscillations in both reactor temperature and concentration. Proportional feedback control of the reactor temperature to regulate the coolant flow can, however, be used to stabilise the reactor. With positive feedback control, the controller action reinforces the natural oscillations and can cause complete instability of operation. 

Jaffrezou, J. P., Maestre, N., de Mas-Mansat, V., Bezomhes, C., Levade, T., and Laurent, G., 1998, Positive feedback control of neutral sphingomyelinase activity by cerattride. Faseb J 12 999-1006. 

ATP exerts negative feedforward control (contrast with Example 9.7), while ADP exerts positive feedback control. 

Gaitonde, N.Y. J.M. Douglas. 1969. The use of positive feedback control systems to improve reactor performance. AIChE J. 15 902-10. 

Eaily research with simple bimanual rehabilitators indicated that simple proportional position feedback control laws can te used to assist in impaired movements. - In this scheme, the controller specified an actuator force proportional to the error between a reference trajectoiy and the actual movement trajectory. The reference trajectory was chosen as the normative or desired trajectory for the limb, llius the more the limb deviated from the desired trajectory, the more force was provided by the rehabilitator to drive the limb toward the desired trajectory. The firmness of the assistance was determined by the gain of the position controller. 

Feedback Control In a feedback control loop, the controlled variable is compared to the set point R, with the difference, deviation, or error e acted upon by the controller to move m in such a way as to minimize the error. This ac tion is specifically negative feedback, in that an increase in deviation moves m so as to decrease the deviation. (Positive feedback would cause the deviation to expand rather than diminish and therefore does not regulate.) The action of the controller is selectable to allow use on process gains of both signs. 

On springless actuators where the actuator is not usable for throttling control without position feedback,... 

Here Kc = 0 represents open loop conditions, Kc < 0 represents positive feed back conditions, and Kc > 0 represents conventional negative feedback control. 

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