Riaan Stopforth

Quad-Rotor Unmanned Aerial Vehicle Helicopter Modelling & Control

This paper presents the investigation of the modelling and control of a quad-rotor helicopter and forms part of research involving the development of an unmanned aerial vehicle (UAV) to be used in search and rescue applications. Quad-rotor helicopters consist of two pairs of counter rotating rotors situated at the ends of a cross, symmetric about the centre of gravity, which coincides with the origin of the reference system used. These rotors provide the predominant aerodynamic forces which act on the rotorcraft, and are modelled using momentum theory as well as blade element theory. From this, one can determine the expected payload capacity and lift performance of the rotorcraft. The Euler-Lagrange method has been used to derive the defining equations of motion of the six degree-of-freedom system. The Lagrangian was obtained by modelling the kinetic and potential energy of the system and the external forces obtained from the aerodynamic analysis. Based on this model, a control strategy was developed using linear PD controllers. A numerical simulation was then conducted using MATLAB® Simulink®. First, the derived model was simulated to investigate the behaviour of the rotorcraft, and then a second investigation was conducted to determine the effectiveness of the implemented control system. The results and findings of these investigations are then presented and discussed.

Development of an UAV for search & rescue applications

In the event of a disaster, there is an impending need for robotic assistance in order to conduct an effective search and rescue operation, due to their immediate permissible deployment. In this paper, the development of an unmanned aerial vehicle (UAV) intended for search and rescue applications is presented. The platform for the UAV is a quad-rotor type helicopter, simply referred to as a quadrotor. A plan for the mechatronic system integration was devised to combine the mechanical, electronic and software elements of the research. Once the system was modelled mathematically, a control strategy was implemented to achieve stability. This was investigated by creating a MATLAB® Simulink® numerical model, which was used to run simulations of the system.

A 7 DOF exoskeleton arm: Shoulder, elbow, wrist and hand mechanism for assistance to upper limb disabled individuals

This paper illustrates the mechanical structures spherical motion, kinematic matrices and achievable workspace of an exoskeleton upper limb device. The purpose of this paper is to assist individuals that have lost their upper limb motor functions by creating an exoskeleton device that does not require an external support; but still provides a large workspace. This allows for movement according to the Activities of Daily Living (ADL).

R2T2: Robotics to integrate educational efforts in South Africa and Europe

This paper presents the first cross-continental collaborative robotic event based around education. It was entitled R2T2 and it involved more than 100 children from Europe and Africa. Based on remo...

A Portable Passive Physiotherapeutic Exoskeleton

The public healthcare system in South Africa is in need of urgent attention in no small part because there has been an escalation in the number of stroke victims which could be due to the increase in hypertension in this urbanizing society. There is a growing need for physiotherapists and occupational therapists in the country, which is further hindered by the division between urban and rural areas. A possible solution is a portable passive physiotherapeutic exoskeleton device. The exoskeleton device has been formulated to encapsulate methodologies that enable the anthropomorphic integration between a biological and mechatronic limb. A physiotherapeutic mechanism was designed to be portable and adjustable, without limiting the spherical motion and workspace of the human arm. The exoskeleton was designed to be portable in the sense that it could be transported geographically. It is a complete device allowing for motion in the shoulder, elbow, wrist and hand joints. The inverse kinematics was solved iteratively via the Damped Least Squares (DLS) method. The electronic and computer system allowed for professional personnel to either change an individual joint or a combination of joints angles via the kinematic models. A ramp PI controller was established to provide a smooth response to simulate the passive therapy motion.

Performance of the Improvements of the CAESAR Robot

Robots are able to enter concealed and unstable environments inaccessible to rescuers. Previous Urban Search And Rescue (USAR) robots have experienced problems with malfunction of communication systems, traction systems, control and telemetry. These problems were accessed and improved in developing a prototype robot called CAESAR, which is an acronym for Contractible Arms Elevating Search And Rescue. Problems encountered with previous USAR robots are discussed. The mechanical, sensory and communication systems that were used on CAESAR are briefly explained. Each system was separately tested by performed experiments. Results of field tests and the robot performance experienced during a disaster scenario that was created are discussed. The capabilities of CAESAR are explained in these tests to determine if some of the problems experienced previously are solved.

Customizable Rehabilitation Lower Limb Exoskeleton System

Disabled people require assistance with the motion of their lower limbs to improve rehabilitation. Exoskeletons used for lower limb rehabilitation are highly priced and are not affordable to the lowerincome sector of the population. This paper describes an exoskeleton lower limb system that was designed keeping in mind that the cost must be as low as possible. The forward kinematic system that is used must be a simplified model to decrease computational time, yet allow the exoskeleton to be adjustable according to the patients leg dimensions.

An overview and comparison of upper limb prosthetics

This paper looks at various existing upper limb prostheses both from the commercial and research area. It assesses what has been achieved in the commercial field as well as its shortcomings. State-of-the-art research on upper limb prosthetics is reviewed and the progress over the last decade is touched on briefly. The paper then considers haptic feedback and myoelectric control, two cutting-edge technological fields within the field of prosthetics. A comparison is made between current and past upper limb prostheses and improvements to these prostheses are discussed. Suggestions for future work are made to incorporate and develop haptic feedback and more advanced control algorithms to further improve the current prosthetics. Myoelectric control is identified as the most limiting factor to the progress of upper limb prosthetics.

Robots for Search and Rescue Purposes in Urban and Underwater Environments - a survey and comparison

Modern technology has provided robots that can be used for Search and rescue purposes where rescuers have difficulty to locate victims. This is due to problems such as visibility and different environmental conditions. The autonomous mobile ability of robot vehicles makes them ideal platforms for search and rescue purposes. Improvements in communication, navigation and sensory systems provide for efficient mobile robotic platforms. The paper describes two platforms that use similar technologies, but have different applications and operate in different environments. Semi-autonomous and autonomous robots for search and rescue operations also use similar technology to achieve different goals. The way this technology is used can be similar due to the harsh environment that the robots will be entering. Comparisons of the two robots are discussed as to the different modules and material that will be needed for each robot.

Sensory system integration of the designed mechatronics Touch Hand

Purpose – This paper aims to explore the electronic design of the Touch Hand: a low-cost electrically powered prosthetic hand. The hand is equipped with an array of sensors allowing for position control and haptic sensation. Pressure sensors are used on the fingertips to detect grip force. A temperature sensor placed in the fingertip is used to measure the contact temperature of objects. Investigations are made into the use of cantilever vibration sensors to detect surface texture and object slippage. The hand is capable of performing a lateral grip of 3.7 N, a power grip of 19.5 N and to passively hold a weight of up to 8 kg with a hook grip. The hand is also tested on an amputee and used to perform basic tasks. The amputee took 30 min to learn how to operate the hands basic gripping functions. Design/methodology/approach – Problems of previous prosthetic hands were investigated, followed by ways to improve or have similar capabilities, yet keeping in mind to reduce the price. The hand was then designed,...