Sawmill optimization and control with Acuity laser scanners

Concept Systems has designed an integrated sawmill optimization system consists of two Acuity laser scanner systems, one to measure the sweep of the log and the other to determine the face structure of the log. Each system is independent, and reports its findings both to a remote operator as well as the PLC system over Ethernet.

The Sweep Scan system is tasked with finding logs less than 22ft which have less than 4 inches of sweep and are less than 15 inches in diameter. Since we are looking for straight logs, only one scanner is required (the log is assumed to be tight against the belt).
The system is set to 50K Samples per second and the mirror speed is set to 2000 RPM, with a conveyor speed of approximately 360 fpm. The scanner points straight down, and the log passes directly underneath the scanner at a distance of four feet in full daylight. The only other sensor involved is an encoder to determine the conveyor movement. Using the scanning capabilities of the AR4000 and the 200KHz card, both the laser encoder and the belt encoder are reported with the readings to develop slices of the log. The slices are then analyzed using interpolated “ideal” locations of the slices relative to their actual locations, to determine log “sweep” or side to side to side log growth. The log diameter is taken by determining the point in the scan that is closest to the laser for each slice. The length is determined by a presence/absence method of looking at slice data. With this data, the system compares the sweep, diameter, and length against a set of constraints, and determines of the log should be kicked directly to the mill, or should enter the bucking line
.

The Face Scan system is tasked with determining the real shape of the face of the log. The log is transferring to the chopsaw, and approximately 8ft prior to the saw, a scanner is mounted at a 45 degree angle against the flow of the log. The scanner is also an AR4000 with a 200Khz card scanning at 50Khz with both the mirror encoder and the belt encoder being tracked with the readings. As the log progresses through the scanner, a profile of the face is created, and using a proprietary mathematical model, the system determines the optimum face cut to render approximately 80 percent of the log to a square shape. Once the solution is determined, the system compares it to a set of constraints (a minimum cut, as well as a determination based upon the remaining fiber from the optimizer) and determines if a face cut should be made. If the face cut is determined to be made, then the log is slowed down and positioned under the chopsaw using closed loop motion control, and automatically cut. Once made, the log is automatically processed as usual.

Both systems communicate directly to the Allen Bradley ControlLogix processor using TCP/IP, and both systems automatically report their status as well as graphical representations of their field of view to the operator interface using socket based TCP/IP communications from one system to the other.

Both systems run entirely in automatic, and do not require any operator intervention to function. In addition, both systems are completely rated for outdoor use and operate in a full sun/rain/snow environment with only provisions to keep snow and ice from accumulating in winter and direct sun from heating the system enclosures in summer.

For more information, contact