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In order to use computer to carry out quick, accurate and economic design of product shape and colour, a package of AUTOLISP programs was developed which can be run under AUTOCAD main environment. Due to the limitation of AUTOCAD 11.0 and 12.0 in 3-D design of complex curved surface, the 3-D design functions were enhanced in the following aspects: (1) 3-D line JOIN and BREAK commands were developed to join and break 3-D polylines. SPIRAL command was designed to create 3-D cone or cylindrical spiral line. In addition, EFTURN and MEFTURN commands were developed to change the vertex sequence of polyline totally or midway. (2) 3-D elements and characters Existing subroutines were revised to directly generate Box, Cone, Pyramid, Dome or Dish, Torus, Sphere and Wedge ready for solid modeling. Furthermore, CONVEX, HOLE and TUBE commands were developed to generate different kinds of convex, hole and tube respectively.

In much heavy industrial equipment, power transfer is primarily provided by a hydraulic system. Reliable operation of a hydraulic circuit can only be ensured through proper design, effective maintenance and continuous monitoring. Each of these areas requires the expertise of well-trained and experienced individuals. Unfortunately such individuals are not always available. However, the recently introduced technology of “expert” or “knowledge-based” systems can make these individuals' expertise available in the form of a computer program. As part of a long term project in the application of expert systems to hydraulic circuit design, a prototype program has been developed which can successfully configure a variety of circuits including multiple load and add-on circuits. This is currently being expanded to include sequenced circuits, steady-state circuit analysis, which would include component sizing, and dynamic analysis.

In many areas, neural network technology has made a successful transition from theory to practical application, primarily due to the advances that have been made in computer technology and digital signal processing. Research at the University of Saskatchewan over the past few years has focused on applying neural network technology to fluid power systems. This paper will examine four projects that have been initiated by the authors and their graduate students which use neural networks for purposes of open loop pattern following, multiple input - multiple output control, indirect measurement of actuator displacement, and hydraulic component identification. A brief introduction to static and dynamic neural networks is given. Descriptions of the individual project objectives, the experimental implementation of neural networks to achieve these objectives, and some typical experimental results are considered.

Understanding the Relationships between plants and soil is important in the development of methods of crop production. Although physical properties of soil conducive to plant growth can be recognized by experienced observers, many of these properties have not been defined satisfactorily in mathematical or physical terms. A method of measuring penetration resistance and energy exerted by a mechanical seedling (a steel probe simulating a seedling) as it moved upward through the soil surface under different levels of surface compaction and soil moisture was examined. Mechanical seedlings with 2.06, 3.19 and 4.65 mm tip diameters were tested at soil moisture levels of 13, 17, and 20%. The penetration rate of the mechanical seedling while moving through the soil was held constant at 10 mm/min. Results showed that the emergence energy increased directly with soil surface compaction pressure, initial soil moisture content, and mechanical seedling diameters.

Variable rate nitrogen fertilization (VRNF) is a technique being developed for agricultural applications in recent years. In designing a controller for VRNF system, it is hoped that the process parameters, which are difficult to measure, could be identified on-line so that the model-based digital controllers or adaptive controllers could be used to achieve better system performance. In this paper, the problems associated with the on-line process parameter identification for the control of variable rate nitrogen fertilization are analyzed. Simulation studies and experimental tests were conducted to determine a suitable parameter estimation algorithm and the influence of pseudo random binary signal and external torque disturbance on the parameter identification accuracy. The results from the simulation and experimental studies revealed that the recursive least square algorithm is most suitable for parameter estimation.

A hydrostatic actuation system referred to as the Electro Hydraulic Actuator (EHA) has been designed and prototyped. In this paper, a mathematical model of the EHA is reviewed and analyzed. This theoretical analysis is supported by open-loop experimental results that indicate the presence of nonlinearities but at a degree that is considerably less than that of conventional hydraulic systems with servo-valves. The behavior of the system can be approximated as piece-wise linear with the damping ratio and natural frequency changing according to a piece-wise operating region. The EHA model is used in conjunction with experimentation and numerical optimization for quantifying the influence of unknown parameters in this system. A parametric model for the EHA is subsequently proposed and validated.

This paper compares the characteristics of a high-precision hydrostatic actuator to that of conventional hydraulic systems using servovalves. Servovalve controlled hydraulic actuators retain their market share as they provide precision movement and offer a very high torque to mass ratio at the final actuation point. The input current/output torque relationship of a conventional hydraulic actuation system is reviewed in a robotic context. This relationship is summarized by a mathematical model that can be expressed in a generalized form. This model is used for the analysis of flow and dynamic characteristics. The design and modeling of a recently proposed high-performance hydrostatic actuation system referred to as the ElectroHydraulic Actuator (EHA) is briefly reviewed. A prototype of this actuator has been produced and has demonstrated a comparable performance to servovalve controlled conventional hydraulic systems.

Pulse width modulation (PWM) has been used to alter the performance of on-off hydraulic control valves to make them perform as proportional type flow control valves. Nonlinear performance resulting from time delays in valve switching as well as valve wear due to continuous cycling continue to persist as operational problems. This paper examines a new technique called modified PWM control. The method was found to provide accurate control with a minimum of valve chatter.

Most fertilizer application systems are not capable of variable rate adjustments “on-the-fly”. To change the application rate, the farmer must dismount the tractor and change the gear ratio mechanically (i.e. via gears, chains, etc.). Air seeder manufacturers have come up with their own unique solutions to address this problem, usually involving electrohydraulics. At present there are older seeding units that perform adequately, but do not have the variable rate option. A retrofit is therefore very desirable for these units. In this paper, the feasibility of a simple hydraulic proportional valve and variable speed motor circuit is employed to replace the gears and chains. The unit is integrated with a microcontroller to provide compensation to the nonlinear properties of a proportional valve, and in turn provide a very accurate feedrate. In addition, direct user input from the cab of the tractor is possible, allowing on-the-go rate changes.

This paper describes the design strategy adopted for developing a new high performance actuation system referred to as the ElectroHydraulic Actuator (EHA). The design approach can be divided into fives phases that include: pre-conceptual analysis, conceptual design, preliminary design, detailed design and, integration and test. An important aspect of the design process is the use of modeling and simulation for the analysis, sizing and selection of off-the-shelf parts, and for the detailed design of new custom made components. EHA is based on hydrostatic transmission. It is a unique device with its own characteristics and requires hydraulic components that are specifically tailored to its needs. A prototype of EHA has been produced and has demonstrated an extremely high level of performance. The performance of this prototype complies with design requirements and validates the chosen design approach.

The Nexus vehicle was designed and built for Transport Canada at the University of Saskatchewan to demonstrate that a safety compliant single passenger commuter vehicle could attain extremely low fuel consumption rates at modest highway speeds. Experimentally determined steady state fuel consumption rates of the Nexus prototype ranged from 1.6 L/100 km at 61 km/hr up to 2.8 L/100 km at 121 km/hr. Fuel consumption rates for the Society of Automotive Engineers (SAE) driving cycle tests were 4.5 L/100 km for the SAE Urban cycle and 2.0 L/100 km for the SAE Interstate 55 cycle. The efficiency of the power train was determined using a laboratory dynamometer, enabling the road test results to be compared to the results from an energy and performance simulation program. Predicted fuel economy was in good agreement with that determined experimentally. Widespread use of single passenger commuter vehicles would substantially reduce current transportation energy consumption.