| Author | Tran Ngoc Thanh |
| Call Number | AIT Diss. no.AE-80-01 |
| Subject(s) | Tractors--Dynamics
|
| Note | A dissertation submitted in the partial fulfillment of the requirements for the degree of Doctor of Engineering. |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. AE-80-01 |
| Abstract | Present draft control systems exhibit poor depth performance when the tractor-implement os to work on undulating ground. The implement may lift over the ground surface or go deep into the soil, thus causing excessive depth variation. A model for a draft control system was therefore developed. Experiments were carried out to verify it and suggestions were made for the improvement of the performance of draft control systems. In a draft control system, the control is activated by the soil force on the implement. When the implement goes down, draft increases. The implement is lifted. On the contrary, if the implement goes up, draft reduces and the implement will be lowered. The rate of lift or lowering is a function of control valve displacement and pressure inside the ram cylinder, called system pressure. Forces on the tractor-implement combination determine traction coefficient which affects the working speed. Working speed, depteh, rate of implement movement in turn determine the soil force on the implement. Assumptions made in constructing the model included: the horizontal soil force varies linearly with depth; the vertical soil force is proportional to the product of horizontal soil force and the angle the plough makes with its direction of movement; the system pressure varies linearly with vertical force on the plough; and the inertia force is negligible. A computer program for the draft control system was developed. It is written in computer simulation language CSMP III (Continuous System Modelling Program). Experiments to verify the model developed were conducted with a three-furrow mounted mouldboard plough in heavy soil, the control system being top link sensing. To impart an artificial depth variation which serves as an input to the control system, the two tractor rear wheels were made eccentric. To measure soil forces acting on the implement, a three-point linkage dynamometer was constructed. The dynamometer consists of two lower and one top beam transducers to detect the vertical and horizontal components of soil force. Calibrations were done for each beam transducer and also for the whole dynamometer in situ to ensure its proper functioning in actuarial field measurements. The system pressure was measured by a pressure transducer connected directly to the ram cylinder. The plough position relative to the tractor was determined by a displacement transducer and the tractor speed was monitored by a pulse generator attached to the front wheel. The computed results correspond fairly well with the experimental ones in all experimental runs. The validity of the model developed was further strengthened in experiments on variation of two system parameters, namely, the rate of lowering and sensing spring stiffness. The coefficient of variation of draft is used as the criterion in comparing experimental and predicted results. The computed coefficients of variation of draft correspond well with the experimental ones: draft variation is high at low rates of lowering and low spring constants; draft variation reduces at their medium values but again increases for high rates of lowering and high spring constants. |
| Year | 1980 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. AE-80-01 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Agricultural and Food Engineering (AE) |
| Chairperson(s) | Singh, Gajendra; |
| Examination Committee(s) | Gee-Clough, David;Balasubramanian, N. V.;Jindal, Vinod K.;Konaka, Toshio;Balasubramanian, A. S.; |
| Scholarship Donor(s) | Canadian Government; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 1980 |