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About this book

This book examines the driving dynamics of harvesting machines with large harvesting heads. It looks at how to efficiently use these machines. The author explores a common problem that hinders machine performance when harvesting with very large headers. He deals with concepts for reducing the undesired effects of vehicle dynamics when using these machines.

With the steadily increasing capacity of harvesting machines, the working widths of the harvesting heads get wider and the headers get heavier. It has become essential with these giant headers to use header height sensors and header control systems to avoid the headers from being run into the ground when encountering elevation changes in the terrain. A fundamental limitation of the viable speed of header height adjustments arises from the combination of the wider and heavier headers with soft agricultural tires.

The current solution to find an appropriate speed of header height adjustments is to perform a header calibration whenever a new header is attached to the machine and to endow the machine operator with the capability to tweak the speed of adjustments manually. The result of an inappropriate speed of height adjustments is a reduction in overall productivity and an under-utilization of the harvesting machine. The author looks at ways to prevent this. He offers detailed modeling of the vertical dynamics including dynamic wheel loads. In addition, the book contains results from simulations and machine tests.

Table of Contents


Chapter 1. Introduction

This chapter introduced the reader to the improtance of precision farming and automation for the development of efficient agricultural machinery. Further on, it gives a brief introduction to self-propelled harvesting machines and the state of the art in harvester header control. Hereto, the basic structure of a header control system, the modes of header operation, different header height sensing concepts, as well as different control approaches are described. The chapter ends with an explanation of the approach and the structure of this book.

Benedikt Jung

Chapter 2. Vehicle dynamics modelling and model analysis

This chapter is dedicated to the vertical dynamics modelling and the model analysis of a self-propelled harvesting machine. It contains the modelling assumptions, and presents the vertical dynamics model of the harvesting machine in great detail. The model includes the harvesting machine, the harvesting head, the hydraulic raise/lower circuit of the front-end equipment and the dynamic wheel loads resulting from accelerating and decellerating of the vehicle. Additionally, the linearisation of the model is described. In the model analysis, it is shown how the natural frequencies and according damping ratios of the harvesting machine are derived, and a sensitivity analysis is performed. The chapter ends with a discussion of potential solution approaches to the header height control problem under investigation

Benedikt Jung

Chapter 3. Proactive vehicle oscillation suppression

This chapter illustrates how the undesired effects of the harvesting machine dynamics can be cancelled out with proactive vehicle oscillaiton suppression. The reader is first introduced to the basic idea of the proactive vehicle oscillation suppression with a strong focus on command shaping techniques. Different command shapers are discussed and weighed based on the application’s performance criteria. Furtheron, it is explained why an adaptive command shaping method is most promising for the header height control problem and an adequate adaptation scheme is chosen from a selection of the most prominent identification methods. The chapter also contains a section about the choice of the input signals for the adaptation scheme by the example of a combine harvester, the signal pre-processing and the determination of the order of the estimator model. In addition, it is explained how the natural frequency and damping ratio is derived from the coefficients of the estimator model. The chapter ends with a step-wise validation of the adaptive command shaping concept with real machine data.

Benedikt Jung

Chapter 4. The vehicle speed as additional actuator

This chapter introduces the idea of using the vehicle speed as an additional actuator in the header height control problem. Based on the HAUTUS tests, the impact on the controllability of the system is investigated. Further on, considerations regarding limitations of the viable range of vehicle speed changes are presented. Finally, it is shown how the vehicle speed is included in the header height control problem and the concept is validated by means of the plant model in the simulation environment.

Benedikt Jung

Chapter 5. Key conclusion and future work

This chapter summarizes the content of each chapter briefly, presents key conclusions and suggests future work.

Benedikt Jung


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