Abstract: A method is disclosed for automatic estimation of backlash in a control system which includes a controller and a process to be controlled, wherein said controller is capable of performing integrating control of said process using one or more controller parameters to control a process output signal of said process with respect to a setpoint value thereof. The method involves monitoring said process output signal to determine a value reflecting momentary differences between setpoint value and actual value of said process output signal during a time interval; and estimating the backlash from said determined value and said one or more controller parameters.

Abstract: A method is disclosed for automatic estimation of backlash in a control system which includes a controller and a process to be controlled, wherein said controller is capable of performing integrating control of said process using one or more controller parameters to control a process output signal of said process with respect to a setpoint value thereof. The method involves monitoring said process output signal to determine a value reflecting momentary differences between setpoint value and actual value of said process output signal during a time interval; and estimating the backlash from said determined value and said one or more controller parameters.

Abstract: A method for evaluating whether a measurable disturbance on a process controlled by a feedback controller is suitable for feed-forward control. The disturbance is measured. The controller output signal due to the disturbance is measured. A first reference signal corresponding to the controller output signal is measured when responding to disturbance entering before the process. A second reference signal corresponding to the controller output signal is generated when responding to a disturbance entering after the process. It is estimated where in the process the disturbance enters by comparing the measured controller output signal due to the disturbance with the reference signals. It is evaluated whether the disturbance is suitable for feed-forward control depending on where in the process the disturbance enters.

Abstract: A method for evaluating whether a measurable disturbance (d) on a process (1) controlled by a feedback controller (2) is suitable for feed-forward control, characterized in that it comprises the steps of measuring said disturbance, measuring the controller output signal (u) due to said disturbance, generating a first reference signal (7) corresponding to the output signal from the controller when responding to a disturbance entering before the process, generating a second reference signal (8) corresponding to the output signal from the controller when responding to a disturbance entering after the process, comparing the measured controller output signal due to the disturbance with the reference signals, and evaluating whether the disturbance is suitable for feed-forward control depending on said comparison.

Abstract: A method for compensating for static friction in an actuating device includes the steps of generating an actual signal y2(t) corresponding to a quantity which is controllable by the actuating device, generating a set value signal y1(t) generating a control signal s1(t) based on the set value signal y1(t) and the actual value signal y2(t), and supplying the control signal to the actuating device for controlling the same. The method also includes the steps of generating an intermittent signal s2(t) compensating for friction, sensing the sign of the derivative with respect to time of the control signal s1(t), giving the signal s2(t) compensating for friction the same sign as the derivative, and adding the signal s2(t) compensating for friction to the control signal s1(t) before supplying the same to the actuating device.

Abstract: Method for adjusting the setting of a digital process regulator on the basis of the result obtained from a simple relay feedback experiment. When an adjustment of the regulator setting is to be made, the relay feedback is connected in the control feedback circuit instead of the regulator in order to cause self-oscillation. The self-oscillation signal is utilized to calculate the new setting of the regulator.

Abstract: In tuning a regulator (2) of the PID-type of a process (1) in a feed back system where the process and the regulator has a transfer function G(s) in common, a method is proposed for bringing the system into self oscillation for measuring the amplitude and frequency of the oscillation and tuning the regulator in dependence of the measurements obtained. A circuit function (NL) having non-linear characteristic and a describing function N(A) is introduced into the system in series to the process for acting on the regulator signal (e). Self oscillation is obtained if G(i.omega.).multidot.N(A)=-1 for at least one value of the angular frequency .omega. and the amplitude A of the regulator signal (e). An apparatus for performing the method is disclosed.