US 4,038,531 A · Process control apparatus for controlling a particleboard manufacturing system

Abstract

An improved particleboard manufacturing system wherein the weight of each mat for forming a particleboard is continuously monitored and controlled by a process controller as the mats are formed on a moving conveyor. The actual weight of each mat is determined and utilized by the process controller to selectively control the speed of the conveyor and the rate at which wood particles are deposited by a series of formers that are located along the conveyor system to thereby control the weight of mats currently being produced. The process controller includes a control system for continuously controlling mat weight by supplying former speed control signals that are related to a predicted weight error signal, developed within the control system, and a measured weight error signal equal to the difference between a desired or target weight and the actual weight of each mat. A signal, equal to the difference between the measured error and the predicted error, is conditioned by a transfer function unit to supply a signal suitable for driving each former of the particle board manufacturing system. To provide a near optimal control system, the signal conditioning supplied by the transfer function unit is adaptively tuned on the basis of the measured weight error. A second control system is included in the process controller to provide automatic mat weight control whenever the system operator changes the production rate by altering the speed of the conveyor system. During such changes in production rate, this control system modifies the former speed based on changes in conveyor speed. A third control system, contained within the process controller, permits the controlled particleboard manufacturing system to be efficiently changed from the production of one grade of particleboard to another grade while minimizing the number of unacceptable mats that are produced. The process controller also includes a fourth control system that allows the controlled particleboard manufacturing system to be reactivated after a brief interruption in production without producing a large number of mats of an unacceptable weight.

Claims21

Dependent claims

In a particleboard manufacturing system wherein mats having a predetermined length and width dimension are formed on a moving conveyor by a plurality of formers arranged to deposit a volume of resin coated wood particles for forming a web of loosely bonded wood particles, said web being trimmed to form said mats, the speed of said conveyor and the volume of said wood particles deposited by each of said formers being controllable by electrical signals to thereby establish the weight of each of said mats, the improvement comprising:

weight control means for automatically controlling the weight of each mat produced by said manufacturing system, said weight control means including means for detecting the weight of each of said mats;
means for detecting the weight error between the weight of each of said mats and a predetermined target weight, prediction means for determining a predicted weight error for each of said mats being produced by said system, said prediction means responsive to the difference between said weight error and said predicted error for each of said mats supplied by said manufacturing system;
means for determining said difference between said weight error and said predicted error;
signal conditioning means responsive to said difference between said weight error and said predicted weight error of each of said mats, said signal conditioning means supplying a control signal having a predetermined mathematical relationship with said difference between said weight error and said predicted weight error of each of said mats;
and
means responsive to said control signal for supplying said electrical signals to at least one of said formers to control the weight of said mats.

3 more elements

Process control apparatus for controlling a particleboard manufacturing system wherein mats having a predetermined length and width dimension are formed on metal cauls moving along a conveyor and transported beneath a series of formers for depositing a volume of wood particles, the speed of said conveyor and the volume of wood particles deposited by each of said formers being controllable by electrical signals, said process control apparatus comprising:

weight determining means for supplying a first signal representative of the weight of each of said mats deposited by said formers of said particleboard manufacturing system as each of said cauls reaches a predetermined point along said conveyor;
first subtractor means for supplying a second signal representative of the difference between the weight of each of said mats and a predetermined target weight;
second subtractor means responsive to said second signal and an applied third signal for supplying a fourth signal representative of the difference between said second and third signals, said second subtractor means supplying said fourth signal each time one of said mats causes said weight determining means to supply said first signal;
transfer function means responsive to said fourth signal for supplying a control signal to control the rate at which at least one of said formers deposits said wood particles, said transfer function means supplying said control signal in accordance with a predetermined algebraic expression;
and
predictor means for supplying said third signal to said second subtractor means, said predictor means including means for storing a predetermined number of values representative of the desired response of said manufacturing system to said control signal supplied by said transfer function means, means for supplying said values as scaler portions of each of said fourth signals, and means for supplying said third signal as an accumulated sum of all previously supplied third signals and the difference between the current fourth signal and one of said stored values.

3 more elements

Dependencies are inferred from the claim text.

Process control apparatus for controlling a particleboard manufacturing system

Life of this patent

Process control apparatus for controlling a particleboard manufacturing system

Life of this patent

Abstract

Claims21