Ergonomic Design Modification, Testing and Evaluation of Pedal Operated Paddy Thresher
4.3 Computer-Aided Design and Digital Human Modeling
have undergone many changes across different locations. The general failure of existing pedal threshers is likely due to their operational difficulty and heavy weight. The NER topogeography is somewhat different from other parts of the country. Therefore, transportation of heavy equipment in hilly areas is quite difficult.
1 - Rear grain shield and back supporting frame; 2 - Pedal; 3 - Crank and pinion gear; 4 - Connecting rod; 5 - Pedal shaft; 6 - Rocker assembly; 7 - Spike tooth; 8 - Tie member; 9 - Side grain shield; 10 - Side supporting frame; 11 - Threshing cylinder.
Fig. 4.3 Typical appearance of pedal operated paddy thresher
DHM. Extensive literature review revealed that conventional design methodologies are gradually converted to modern techniques in diverse fields. Basic approaches in problem solving during development of agricultural equipment could be divided in two categories (Fig. 4.4). The conventional approach allows the engineer to design and conduct repetitive field experiments to determine the best combination of independent variables needed to obtain the required output. Problem associated with this approach is that, designers can only guess how operator would interact with the product. Moreover, it is time consuming, more costly and sometimes further modification is almost impossible.
The second approach is computer-aided design, considered the best one – where equipment designer and manufacturer can effectively interact with the product model directly in 3D CAD environment, rather than conventional on-paper 2D interactions during the process of conceptual modeling (Kamboj et al., 2012). This offers freedom for any design modification at any stage in the product design development phase prior to production.
Fig. 4.4 Computer aided vs. conventional designing process
4.3.1 DHM in product design and development
DHM provides a computer-generated 3D environment for product design and simulation.
At present, DHM has widespread applications in various applied fields and industries, including agriculture for design of tools / equipment, machines and off-road vehicles (Patel et al., 2013a); with use in human performance assessment and optimizing product
More/high Less/low
design for optimal user-system integration (Dooley, 2012; Antonucci et al., 2013).
Earlier, design of farm equipment used to bypass formal ergonomic considerations, resulting in subsequent occurrence of several potential anomalies to the end-user i.e.
farmers. With the advancing technology, a greater number of features are being incorporated for analysis and simulations on projected designs (Antonucci et al., 2013).
These new expansions offer uninterrupted human factors considerations to perform ergonomic analysis of the products. A combination of CAD and DHM encourages many novel approaches in modeling and simulation. These help to carry out ergonomic evaluations of human-machine interactions (Fig. 4.5) to make more safe, efficient, comfortable and productive work environment for every segment of the population (Paul and Lee, 2011).
Fig. 4.5 CAD and DHM interface in product evaluation
Virtual simulation facilitates evaluation of potential advantages and disadvantages of the design conformations, thus being widely used to reduce costs, time to market, and thus to replace the need for costly physical prototypes (Wu et al., 2012). DHM provide visualizations of anthropometry and biomechanics, such as body posture, reach envelope,
field of view, clearances, load on lumbar spine segments etc., which serve as basic inputs for design analysis and engineering decision making.
4.3.2 Applications of computer-aided design in agricultural engineering
Mechanization of various tools and technique used for production, transportation and processing of agricultural products is a need for sustainable development of agriculture (Pretty, 1995). It is well perceived that using CAD based design approaches will extrapolate the advancement of agriculture thereby boosting rural economy, improving the competitive farm ability, and finally raising the farmer’s economy. To date, conventional agricultural design is gradually transformed into modern digitized design tools (Shuming, 2004). Application of CAD has made design of farm machineries intuitive, flexible yet convenient. Various researchers have already been harvested with the CAD advantages (Fig. 4.6).
Fig. 4.6 Application of computer-aided design in agriculture sector
Analyses of various design considerations like stress, fatigue, weight, durability, damage and safety factors assist designer to determine the paramount promising fabrication design prior to finalize the prototype (Shrivastava and Jha, 2011). Today’s CAD software
is truly beneficial for modelling, rendering, simulation and mechanical analysis; but mostly these are not capable of evaluating human factor issues. For incorporation of ergonomic principles in product / process and workplace design, role of DHM software appears to be inevitable (Patel et al., 2013).
4.3.3 Applications of digital human modeling in agricultural sector
With developing consciousness about safety and ergonomic issues in line of advancing computational techniques, DHM is effectively addressing (and solving) human factor issues in early stage of product life cycle (Beeney and Charland, 2012). DHM is special component in CAD for developing 2D or 3D digital manikin (virtual representation of human) using anthropometric and biomechanical database of intended / targeted user population for successful ergonomic evaluation of product fitted in the workplace.There are numerous databases all over the world for different populations. Selection and recommendation of apt anthropometric and biomechanical database are context-specific, and therefore depend on the intended user group using the product / workstation. Use of percentile anthropometric and biomechanical dataset from identified database is a common practice in this regard. DHMs tools help in building complete digital humans (realistic reproduction of body measurement with incorporation of biomechanical features), which is subsequently interfaced with CAD models of product and workplaces in digitally rendered environments to explore the ergonomic consequences viz. human size-scaling, posture analysis, motion analysis, reach analysis, vision analysis etc. (Patel et al., 2013).
Today, engineering design is in the midst of a paradigm shift, where with the help of DHM, researchers have preliminary focus on interfacing the human with system to achieve better system-to-human compatibility. DHM have a comparatively late entry into agricultural engineering set-up. Most of the available literature reported applications of DHM in off-road vehicles only, specifically for tractor cab. DHM allows designers to build tractor cabs suitable for operators of varying body dimensions. It provides the designers with a biomechanically correct CAD representation of the human body i.e.
manikin, that can be animated to simulate driver postures and behavior (Patel et al., 2013). Now, the question which comes to mind is – how would these technologies prove to be beneficial? This can be illustrated with the example of ergonomic evaluation of structure and function of a 3D tractor cab model (Fig. 4.7).
Fig. 4.7 Schematic representation for ergonomic evaluation of 3D tractor cab model with digital human modeling
Although, hand tools and equipment powered by human are commonly used for performing various agricultural operations, no available literatures revealed any DHM tool perceived for design and simulation of manually handled hand tools and equipment.
Various applications of DHM ergonomics for design, analysis and simulation of farming machineries in 3D virtual environment (Wu et al., 2012; Ying et al., 2010; Fathallah et al., 2009; Lundstrom et al., 2008; Chang et al., 2010; Xiao-yan et al., 2010; Hsiao et al., 2005; Deisinger et al., 2000) are shown in Fig. 4.8.
Database Anthropometric:
static and dynamic dimensions
Biomechanical:
range of motion, force, torque
Comfort range:
single joint and multiple joint
Creating 3D virtual environmental
Digital human model creation Ergonomics analysis and evaluation
Vision analysis:
Interior and exterior visual fields from driver's seat
Reach analysis:
Steering, Foot controls and Hand controls Working posture analysis
Human motion simulation
Clearance and interference Ingress and egress
Other analysis Information:
need identification, design limit selection (design dimensions, materials selection,
cost), 2D sketch and concept development
Digital CAB model
Design variables : Driver seat, Steering, Foot controls, Hand controls, Display
dash board and Various indicators
Documentation management Final design concept and prototype making Redesign and modification
Fig. 4.8 Pictorial representation of DHM applications in agriculture