Eduardo P. Godoy

Design and development of the architecture of an agricultural mobile robot

Parameters such as tolerance, scale and agility utilized in data sampling for using in Precision Agriculture required an expressive number of researches and development of techniques and instruments for automation. It is highlighted the employment of methodologies in remote sensing used in coupled to a Geographic Information System (GIS), adapted or developed for agricultural use. Aiming this, the application of Agricultural Mobile Robots is a strong tendency, mainly in the European Union, the USA and Japan. In Brazil, researches are necessary for the development of robotics platforms, serving as a basis for semi-autonomous and autonomous navigation systems. The aim of this work is to describe the project of an experimental platform for data acquisition in field for the study of the spatial variability and development of agricultural robotics technologies to operate in agricultural environments. The proposal is based on a systematization of scientific work to choose the design parameters utilized for the construction of the model. The kinematic study of the mechanical structure was made by the virtual prototyping process, based on modeling and simulating of the tension applied in frame, using the.

Design and implementation of an electronic architecture for an agricultural mobile robot

A current trend in the agricultural area is the development of mobile robots and autonomous vehicles for remote sensing. One of the major challenges in the design of these robots is the development of the electronic architecture for the integration and control of the devices. Recent applications of mobile robots have used distributed architectures based on communication networks. A technology that has been widely used as an embedded network is the CAN protocol. The implementation of the ISO11783 standard represents the standardization of the CAN for application in agricultural machinery. This work describes the design and implementation of an electronic architecture for a mobile agricultural robot. The discussions are focused on the developed architecture, the wireless communication system for teleoperation and the distributed control based on CAN protocol and ISO11783. The evaluation of the developed system was based on the analysis of performance parameters such as motor response and architectural time delay obtained with the robot operation. The results show that the developed architecture can be applied for teleoperation and distributed control of agricultural robots meeting the requirements for accurate robot movement and an acceptable response time for robot control commands and supervision.

The Benefits of Soft Sensor and Multi-Rate Control for the Implementation of Wireless Networked Control Systems

Recent advances in wireless networking technology and the proliferation of industrial wireless sensors have led to an increasing interest in using wireless networks for closed loop control. The main advantages of Wireless Networked Control Systems (WNCSs) are the reconfigurability, easy commissioning and the possibility of installation in places where cabling is impossible. Despite these advantages, there are two main problems which must be considered for practical implementations of WNCSs. One problem is the sampling period constraint of industrial wireless sensors. This problem is related to the energy cost of the wireless transmission, since the power supply is limited, which precludes the use of these sensors in several closed-loop controls. The other technological concern in WNCS is the energy efficiency of the devices. As the sensors are powered by batteries, the lowest possible consumption is required to extend battery lifetime. As a result, there is a compromise between the sensor sampling period, the sensor battery lifetime and the required control performance for the WNCS. This paper develops a model-based soft sensor to overcome these problems and enable practical implementations of WNCSs. The goal of the soft sensor is generating virtual data allowing an actuation on the process faster than the maximum sampling period available for the wireless sensor. Experimental results have shown the soft sensor is a solution to the sampling period constraint problem of wireless sensors in control applications, enabling the application of industrial wireless sensors in WNCSs. Additionally, our results demonstrated the soft sensor potential for implementing energy efficient WNCS through the battery saving of industrial wireless sensors.

Applied simulation to evaluate the quality of control of networked control systems

A current tendency in the research of fieldbus based control systems such as CAN (Controller Network Area) is the use of networked control systems (NCS). This new approach differs from the traditional fieldbus systems in that the controller and the plant are physically separated and connected through an industrial network. The main challenges related to the development of NCS are the degenerative effects caused by the inclusion of the communication network in the closed loop control system. In order to minimize these effects, simulation tools for NCS have been developed to assist the designer in the study of the network influence in the NCS quality of control. This paper presents the application of two simulation tools in evaluating the quality of control of the NCS that compose a CAN-based research platform. The tools are used to evaluate the main configuration parameter that affects the performance of the NCS platform and to verify how sensitive the control loops are under various timing conditions including different messages sampling times and network delays. Therefore, the results of the simulations lead to the conclusion that despite the messages sampling time is the most significant factor in the design of NCS, its influence was related to the kind of system with bigger effects in NCS with fast dynamics.

CAN-based Platform for the Study and Experimentation on Networked Control Systems (NCS)

Abstract Networked control systems (NCS) are a recent trend in the research of distributed control systems with fieldbus networks such as CAN (Controller Network Area). This new approach differs from the traditional fieldbus systems in that the controller and the plant are physically separated and connected through an industrial network. Studies have been made to evaluate characteristics which are inherent to NCS design such as messages sampling time, information lost on the network and network delays between the sensors, actuators and controllers of the control system that can degrade its performance and destabilize the NCS. With the purpose of facilitating the research and highlighting the fundamental concepts in the area of NCS, a CAN-based platform has been developed. Focused on helping the investigation and experimentation on NCS on graduate courses, the platform can be used to perform tasks for NCS such as analysis, modeling, simulation and control. The architecture proposed for the platform is highly flexible allowing experiments to be conducted for several platform configurations, with different design parameters and controller algorithms. This paper describes our approach to designing this CAN-based NCS platform focusing on the hardware and software implementations and presenting the opportunities and benefits of its use to NCS. Experiments done with the platform confirm its functionality and effectiveness for NCS applications with the CAN protocol.

Sampling time adaptive control methodology for CAN-based Networked Control Systems

Networked Control Systems (NCS) have become a widely considered research topic. This new control approach differs from the traditional fieldbus systems in that the controller and the plant are physically separated and connected through an industrial network. The major challenge of NCS design is the limited data feedback using the communication network (network delays and packet loss), which can degrade the NCS performance or even cause instability. For CAN-based NCS, another important issue is the correct selection of the messages sampling times. In order to mitigate these problems, control methodologies have been developed based on different types of network protocols in conjunction with different strategies to handle the degenerative effects related to NCS. This paper describes our approach to design and evaluate a new control methodology for application in CAN-based NCS. The solution is based on an adaptive PID controller that automatically manages the NCS sampling time, reducing the network utilization rate while maintaining NCS performance and stability. The feasibility and effectiveness of the control methodology are outlined through experimentation on a CAN-based NCS platform, showing significant results in the CAN network utilization reduction.

Design of CAN-based distributed control systems with optimized configuration

A current trend in distributed control systems is the application of communication networktechnologies such as CAN - Controller Area Network. A recent utilization approach ofthese technologies is the networked control systems (NCS). The fundamental challenges inthe development of NCS are the analysis of the network delay effects and the prediction of the timing behavior of the distributed control system. The common parameters that impact the performance of NCS include response time, network utilization and network delays induced by the communication of messages between the devices. In addition, the performance of a NCS is highly dependent on these messages sampling times. A significant emphasis has been put on development and application of methodologies to handle the network delay effect in these systems and improve their performances. This paper presents a detailed timing analysis and a mathematical model to calculate these network delays in CAN-based networks. With the results of this model, the application of a methodology is proposed to minimize the effects of these delays and to achieve the optimization (networkoperation and utilization) of a CAN-based network. A case study of a CAN-based distributed control system in a mobile robot is described to demonstrate the application of the optimization methodology and the utilization of the CAN mathematical model systemized.

Modelagem e simulação de redes de comunicação baseadas no protocolo CAN - Controller Area Network

A major trend in industrial systems is the application of communication networks technologies, such as CAN (Controller Area Network), in distributed control systems. A challenging problem in the development of distributed system based on communication networks is the network delay effects in the performance of the system. This fact has motivated the development of simulation tools and models to calculate these delays, to simulate the timing behavioral and evaluate the performance of these systems. This work presents the development of a mathematical model and a Colored Petri Nets model to the simulation of CAN-based distributed systems. The flexibility and potential obtained with the developed models allow determining and analyzing several performance parameters related to communication network and the distributed control. An example of a CAN-based distributed system applied to perform the control of a mobile robot demonstrates the functionalities of the models and its applicability to the analysis of any CAN application.

Design of the mechatronic architecture of an agricultural mobile robot

Abstract Parameters such as tolerance, scale and agility utilized in data sampling for use in Precision Agriculture required an expressive number of researches and development of techniques and instruments for automation. Highlights the employment of methodologies in remote sensing used in coupled to a Geographic Information System (GIS), adapted or developed for agricultural use. Aiming this, the application of Agricultural Mobile Robots is a strong tendency, mainly in the European Union, USA and Japan. In Brazil, researches are necessary for the development of robotics platforms, serving as a basis for semi-autonomous and autonomous navigation systems. The aim of this work is to describe the project of an experimental platform for data acquisition in field for the study of the spatial variability and development of agricultural robotics technologies to operate in agricultural environments. The proposal is based on a systematization of scientific work used as a basis for the choice of the design parameters utilized for the construction of the model. The kinematic study of the mechanical structure was made by the virtual prototyping process, based on modeling and simulating of the tension applied in frame, using the finite elements method, based on basic concepts of kinematics of mobile robots and previous experiences.

Hydraulic networked control of four wheel steering agricultural robot

In a joint project among research institutions and a private company is being designed and built a multifunctional and modular robotics platform for information acquisition in Precision Agriculture. The robotic platform has as main characteristics four wheels propulsion and independent steering, air suspension and break, adjustable width, span of 1,80m in height, diesel engine, hydraulic system and a CAN-based electronic control system. Several modules can be coupled to the platform: autonomous localization and navigation, computer vision, communication, agricultural parameters sensing, robotic arm, and stabilized stand. The proposed paper presents the four wheels steering distributed control system, based on the difference between the desired and actual position and considering the angular speed of the wheels. The results demonstrate that the distributed control system was simple and efficient, providing suitable steering performance for the platform guidance, and also indicate future work possibilities for the system improvement.