Abstract
The design of an assistive lower limb exoskeleton robot for paraplegic patients that can measure the centre of pressure is presented. In contrast with most biped walking robots, the centre of pressure (CoP) or zero moment point (ZMP) has not been actively used in the operation of exoskeleton robots. In order to measure CoP in our exoskeleton robot, two kinds of force sensor units are installed in the exoskeleton: low profile force sensors in foot modules to measure the human weight transferred to the ground and a load cell at the shank frame to measure the supporting force. The CoP of the exoskeleton robot is calculated from the above force sensors, an inclinometer at the waist, and the positions of 14 DOF exoskeleton joints with an algorithm to change the fixed pivot using a foot contact sensor. Experiments on an able-bodied person wearing the designed exoskeleton and walking on the ground are performed to validate the designed hardware system. Through the experiments, the trajectory of the CoP of the exoskeleton with a wearer are calculated based on the proposed algorithm and it is compared with the value measured by a commercial pressure measurement system.
Highlights
1.1 BackgroundAs a method of providing walking assistance for paraplegic patients, exoskeleton‐type assistive devices have recently received a great deal of attention, since these devices can provide full mobility similar to human walking
Instead of using the zero moment point (ZMP), the centre of pressure (CoP) is used in the assistive exoskeleton for the purposes of detecting the human intention to walk and checking stability in this study
Since we have considered the CoP as a method for determining the intention of a patient to walk, the positions of all the contact points where the forces are transferred from the exoskeleton and the wearer to the ground must be known
Summary
As a method of providing walking assistance for paraplegic patients, exoskeleton‐type assistive devices have recently received a great deal of attention, since these devices can provide full mobility similar to human walking. An exoskeleton device refers to a device that is worn by a user to perform a particular function: augmenting human power, assisting walking, supporting heavy loads, and so on [1,2]. Notable studies on exoskeletons for paraplegic patients have recently been reported in the U.S and Israel. The University of California, Berkeley, and Berkeley Bionics have recently developed eLEGS [3, 4], which is a lower‐extremity exoskeleton. The particular sequences of the sensor signals are used to determine the proper time to be operated according to the human intention to walk while in eLEGS. Exoskeletons are still in the early stages of their development [6]
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