Gemini Navsoft Technologies Inc.

SteerVu™ overview

SteerVu™ software control panels

Features:

Server/Client mode operation
Internet IP-based data communications
GNT auto-steering logic controller (Fuzzy Logic Control algorithms)
GNT GPS RTK processor
Travel path mapping tools
Vehicle on-site calibration tools
Vehicle operation graphic interface
Use of off-the-self GPS receivers

Options:

Single-GPS or dual-GPS system for auto-steering the vehicle
Steering wheel or differential wheel system of the vehicle

SteerVu™ provides the GNT auto-steering logic controller with high-accuracy, high-performance GPS navigation solutions and attitude information. SteerVu™ steers vehicles such as rubber-tired gantry (RTG) cranes, cargo transport vehicles, lawn mowers and tractors using a “map and match” mode of operation. SteerVu™ is designed for use in repetitive navigation applications.

SteerVu™ consists of a Base Server (BaseVu) and a Rover Client (RoverVu). BaseVu is connected with one or more GPS Base Stations. BaseVu receives raw GPS observations from the Base Station(s) in real-time. The status of the Base Station(s) is constantly monitored. RoverVu is installed on a vehicle and is connected with BaseVu. Upon receiving a request from RoverVu, BaseVu transmits the raw GPS observations received from the Base Station(s) to RoverVu.

Map and match programming allows a human operator to map a navigation path by driving the vehicle over the path to be matched while RoverVu is in “map” mode. During map mode, RoverVu records and stores GPS positioning data which allows RoverVu to autonomously reproduce the mapped path. Multiple paths can be mapped and stored for a project site. Each path is uniquely defined by the GPS coordinates within the path. Navigation paths are stored locally in RoverVu memory and can be downloaded to a removable USB flash memory drives.

With the navigation paths stored, the vehicle is capable of retracing the mapped paths whenever necessary. When the vehicle is in the vicinity of the desired path, the operator can select the desired navigation path to be matched from a list of paths saved for the site in RoverVu memory. Once the path has been selected and connection to BaseVu has been achieved, the operator moves the vehicle near the start of the navigation path. The operator then places the vehicle in automatic operation mode and the vehicle enters the navigation path, moving to the desired locations automatically.

The GPS RTK (Real-Time Kinematic) technique allows the vehicle to know precisely where it is on the surface of the earth to a positional accuracy of better than one inch. Under purely robotic control, the vehicle will wander off course due to errors caused by wheel slippage, uneven terrain, and other mechanically-induced errors. RoverVu makes use of its GPS RTK navigation solutions and attitude information to correct for errors in the vehicle control system. In typical conditions where satellite visibility is favourable and the vehicle is well calibrated, the navigation path can be tracked to better than plus or minus two inches.

SteerVu™ specifications

GPS base station update rate	@ 1 Hz
GPS base station data format	RTCM 3.x (industrial standard)
GPS rover update rate	@ 10 Hz (20-100 Hz: optional)
GPS rover data format	GPS manufacturer's proprietary data format (binary, compressed)
GPS solution output rate	@ 10 Hz (20-100 Hz: optional)
Auto-steering command rate	Synchronized with the GPS solution output rate
Vehicle status reading rate	@ 20 Hz or higher
Base server capacity (simultaneous multiple rover clients access)	Typically over 100s rover clients (limited by the computing power of the base server and the bandwidth of Ethernet communications)

Logic Controllers

Logic controllers (i.e., control systems) could be built based upon different control logics as:

1. A programmable logic controller (PLC) is a microcomputer with hardware and software specifically designed to perform industrial control operations. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements.

2. A proportional-integral-derivative controller (PID controller) is a generic control loop feedback mechanism widely used in industrial control systems. A PID controller calculates an error value as the difference between a measured process variable and a desired setpoint. The controller attempts to minimize the error by adjusting the process control inputs.

3. A fuzzy logic controller (FLC) is a control system based on fuzzy logic — a mathematical system that analyzes analog input values in terms of logical variables. Fuzzy logic has the advantage that the solution to the problem can be cast in terms that human operators can understand, so that their experience can be used in the design of the controller. This makes it easier to mechanize tasks that are already successfully performed by humans.

The advantage of FLC compared to PID is that FLC has the capability to control non-linear, uncertain systems even in the case where no mathematical model is available for the controlled system.

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