Search Results

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.

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.

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.

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.

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.

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.