Patients with motor disability sometimes have difficulty using a conventional electric wheelchair, often due to a pathological tremor. Developed by an international group with Etienne Burdet of the Imperial College in London, the Brain Controlled Wheelchair uses a screen with different buttons representing goals. A cap with electrodes is placed on the head of the user to detect the brain activity, which is used to derive the desired action, while sensors on the robot guide it to the desired goal.
Invasive methods involve needles or some form of electrical equipment placed directly inside the body. This allows the measurement of more localised signals, which can also provide for a more granular rate of control. In an experiment performed by the Duke University Medical Centre, an array of 96 hair-thin electrodes was placed in a monkey's brain. The monkey was then trained to use a joystick to position a cursor over a target on a computer screen. In the meantime, the brain activity was recorded and analysed by a computer to predict the motion of the cursor. When the researchers understood the signals they were able to control a robotic arm in the same way that the monkeys' arm was being controlled. The cursor was also now controlled by the brain signals instead of needing joystick control. At one point the monkey realised she did not need to move her arm at all and so, keeping her arm still, she controlled the robot arm using only her brain and visual feedback.
Matthew Nagle became one of the first people to use such a brain-computer interface to restore functionality lost due to paralysis. The electrodes were placed in the motor cortex that controlled his dominant left hand and arm. Although he was paralysed from the neck down, he was able to control a computer cursor and open and close an external prosthetic hand.
Exoskeletons
The goal of robotic suits is to wield very large forces without the need for using joysticks, while also allowing the user to move freely without feeling any hindrance from the exoskeleton surrounding him. This field of development has existed for some time – in the 1960s engineers built an exoskeleton called Hardiman, but such efforts soon encountered the technological limitations of the times. Computers were too slow to control the actuators in response to the wearer's movements, and the batteries and motors were too heavy.
Recent prototypes show that useable exoskeletons are now becoming a reality. Bleex2, developed by the University of California, enables a person to walk and run while carrying a heavy backpack (45Kg at 7,2Km/h). The project's goal is to help soldiers in carrying more weapons and supplies on the battlefield without sacrificing agility. The Sarcos exoskeleton is probably the strongest ever built; in a recent demonstration, a user picked up 84Kg without feeling any force from the payload on their own body. The Sarcos has an onboard combustion engine to deliver the necessary hydraulic power to the joints.
The Japanese company Cyberdyne has more civilian applications in mind, such as nurses helping patients out of their beds or even helping the elderly to walk around. Its Hybrid Assistive Limb project has a HAL-5 soon to be commercially available, costing around $1,000 per month. The device is powered by electrical motors with the computers and batteries packed into small pouches attached to the belt. With the batteries fully charged, the complete robot can be enabled for over 2.5 hours and, of course, the machine doesn't tire the way humans do. While wearing this robotic suit, an adult is able to hold up to 80Kg in weight – nearly double what he can do without it – and they can also perform a leg press of up to 180Kg.
