Motion analysis tackles ergonomic problems

Edited by the Engineeringtalk editorial team Mar 8, 2002

The CodaMotion system is used extensively in research projects conducted by the Department of Design and Technology at Loughborough University.

The CodaMotion system is used extensively in research projects conducted by the Department of Design and Technology at Loughborough University.

Recent research projects using CodaMotion have included an investigation into the forces applied to the body during concrete breaking; a comparative assessment of the use of conventional and extended automotive pedals and a pilot study into the physical nature of jar opening.

The CodaMotion System has been used to help identify differences in posture and movement of upper and lower limbs that relate to driver safety and reaction time in use between two driving positions, comparing the of use of conventional and extended automotive foot controls under simulated driving activity.

One of the main objectives of this task analysis was in response to cases reported in the UK and USA of vehicle users being injured through close proximity to the air bag during inflation.

Pedal extensions, that move the pedal horizontally 120mm forward of its initial position, towards the drivers foot, provide access to foot pedal controls for those who may be pregnant, small in stature, or have a disability, increasing the distance from body to steering wheel (air bag position).

The CodaMotion system used infra-red emitting markers placed over anatomical reference points on the upper and lower limbs and head Samples of each subject's posture were processed and an analysis of their performance involved the position of body segments, specifically upper and lower limbs at the beginning and end of the task (with and without pedal extensions).

The CodaMotion system recorded the flexion/extension at the elbow and the knee, provided measurement references to ankle, hand/wrist, body trunk and head position and made it possible to accurately calculate the reaction times when carrying out an emergency stop (with and without pedal extensions).

The characterisation of the subjects in this manner enabled considered assessment of task performance, with the CodaMotion system enabling a detailed analysis of limb movements, translations or compound movements in particular.

CodaMotion has recently been used in the task and product analysis of an electric breaker tool, to help to provide evidence of the forces applied to the body during concrete breaking.

The primary objectives were to describe postures that assist in maintaining control of the tool and to apply a model of hand and object interaction to ultimately provide recommendations for the redesign of electric breaker tools.

Phase one involved the characterisation of the subject and tool and phase two, the recording of the interaction during a specified task, using CodaMotion technology.

With CodaMotion markers attached to the body of the subject and to the concrete breaker, researchers were able to record the interaction between the two during concrete breaking.

The initial results concluded that the breaker tool was too short, obstructing the view of the tool tip, resulting in poor posture; an adjustable length tool was proposed as the solution along with a reconfiguration of the breaker body.

Also in evidence was the uneven pressure loading and force transmission due to the trigger operation, suggesting the need for a two handed trigger and flattened handles with larger ends.

The problems brought about by vibration transmission via the handles resulted in the recommendation for a vibration spacer or a reduction in the amplitude of the hammer blow.

The aim of a pilot study into the physical nature of jar opening was to document the different techniques used by a range of able bodied male and female subjects as they tried to open one of the packaging types highlighted by a recent DTI report as being difficult to open - a vacuum-sealed fruit jam jar.

The study required the observation and documentation of the different techniques used by a range of male and female subjects as they tried to open vacuum-sealed fruit jam jars and the relationship between the physical characteristics of each subject and their task performance with sample jars.

CodaMotion markers were attached to the upper limbs and head of the subjects to record elbow flexion/extension and forearm/hand position through the wrist.

The three CodaMotion units were set at right angles to each other in three axes.