Using a hypothetical project as an example, we will show you how you can quickly assess and iterate a design within a virtual environment. Before we go any further, let’s look at what DHM is and its key benefits.
What is Digital Human Modelling?
Digital human modelling (DHM) is a tool for simulating human interaction with a product or system within a virtual environment. It enables designers and human factors professionals to evaluate designs using anthropometrically and biomechanically accurate avatars.
Key benefits of DHM
DHM largely replaces the traditional methods of building physical models and then developing a design through a trial and error process. This traditional process is incredibly time consuming and expensive. Another limitation is the sizes and shapes of the participants available to us.
In contrast when we are working with DHM in a virtual model, design changes can be made and their impact assessed within a matter of minutes. Human body dimensions can be scaled individually to accurately represent the extreme users in the target population. Nothing is left to chance as we can comprehensively demonstrate the suitability of a design for all its intended users.
One of the key benefits of DHM is this can all be done in the early design stages, which significantly reduces the cost of any design changes. SYSTRA utilises industry leading Santos modelling software to facilitate DHM assessments. One of the key benefits of Santos is the predictive modelling feature which makes Santos incredibly efficient and allows you to explore design variations quickly. We illustrate how this works in the following example.
Example Design Brief
To integrate a new driver information display within an existing rolling stock cab. The goal of the exercise is to identify a suitable mounting location, that supports the intended use, does not impact on existing controls and operations, and minimises modifications to the existing cab design.
Step 1: Early Human Factors Analysis
Before we position the display in the cab we identify what it is for and how it will be used, in this case we have confirmed that:
- The information displayed will be important, though not safety critical
- The display will be temporarily installed in the cab but it will have a ‘docking station’ that both holds and charges the interface
- The display must be installed in a location that can be viewed by the driver whilst in motion and supports touch screen interaction when the train is stationary
If this were a real project then there is likely to be System and Sub-System requirements that must be considered at this stage. Though more often than not, the HF specialist is required to dig a little deeper and define best practice requirements to help guide the design. It’s this combination of human factors expertise coupled with the DHM software that is so powerful.
For the purpose of this example the following requirements have been defined to help guide the design:
- The display should be located within 60 degrees on either side of the line of sight of the operator’s normal working position so that monitoring can be performed while in motion
- Use of the touch screen should avoid twisting and bending wherever possible to minimise physical load and improve comfort
- The display should not impact upon external viewing requirements, notably signal sighting requirements
Step 2: Creating the physical environment
First the Train Cab – It is possible to import 3D models from a wide variety of modelling software. This model is most often provided by the designer in their preferred file format, which is then converted. Working with the original design files means our assessment is completely aligned with the proposed design. However, for this example, we have a created a train cab using a combination of stock CAD files.
Then the digital avatars – For this example, we have included the industry standard, 5th%ile female, and 95th%ile male to represent our user population of Australian train drivers. Due to the normal distribution of key physical attributes across a population, if you demonstrate that the design is suitable for these extreme users, you in turn demonstrate its suitability for the wider population.
It is worth remembering that whilst someone may be 5th%ile in stature, this does not mean they will be 5th%ile in other key dimensions. The stature of each avatar has been scaled using Australian data from Peoplesize 2020. The software then uses a scientifically validated algorithm to scale each body dimension. Though dimensions can be individually scaled if this is critical to the task under investigation.
Step 3: DHM Assessment
In the following images our 5th%ile female avatar has been positioned in a normal driving position. The viewing cone allows us to position the tablet within 60 degrees of the central line of sight. With a rough placement defined we can then begin to iterate the design and identify the optimum solution.
The next step is to establish model constraints between the digital human and simulated environment (e.g. left finger touching tablet, and eyes focusing on the tablet). Once these constraints have been established you can adjust the model geometry and the digital human will automatically adopt the resultant posture.
In this example the software automatically predicts the avatar posture as the driver information display position is adjusted. Analysis tools, such as the joint range of motion tool, are automatically updated with each movement to allow real time assessment of design solutions.
The same series of assessment can be completed using the opposite extreme of the target user population, a 95th%ile male.
In our train cab example, the final step is to assess any impacts on driving the train and signal sighting. To achieve this, we have incorporated a 3D model with a selection of signals positioned in accordance with Australian standards. Using the Eye View feature, we can quickly assess how the tablet position will impact on external sightlines.
This brief project example illustrates how you can bring your designs alive in a virtual environment. You can quickly evaluate design solutions and provide robust assurance evidence to support your design decisions.
Key service areas
- Rolling stock design
- Control room design
- Design for maintenance
Learn more about why Santos was created in this Q&A with CEO Steve Beck.
Our Human Factors team can use Digital Human Modelling to support you. Please contact Jamie Barton if you would like to know more.