This article is prepared to share detailed information about Acrome’s Stewart Platform. It includes 4 main chapters with the following content:
- General Information; which gives some brief information about product’s history and the development process
- Physical Aspects and Capabilities section provides details on hardware and components’ information of the product
- Deliverables section; gives an overview of the deliverables of the product and also provides information on the initial usage
- Applications section; gives information with typical Use Cases
We will start with sharing general information about the product first.
1) General Information about Acrome’s Stewart Platform
An Accessible, Affordable and Intuitive Hexapod
We covered basic understanding of the Stewart Platforms in our other blog post. In this document we will focus on the specific details of the product.
The Stewart Platform by Acrome blends innovative technology, state-of-the-art materials, and visionary creativity for unparalleled excellence. Each design element is meticulously selected and crafted to provide exceptional performance, reliability, and user experience.
The Stewart Platform is not built with a single design decision and process. It has come to fruition through the hard work of a team of committed engineers and innovators at Acrome with a progressive iterative process.
The collaboration between Acrome and Fotokite exemplifies a focused and iterative development process, where challenges were met with innovative solutions. Acrome began collaborating with Fotokite in 2018 to meet specific positioning requirements for Stewart Platforms (you may check Fotokite Case Study for details). The development process faced challenges, including non-linear sensor outputs and the need for network isolation. Solutions iterated the Stewart Platform models.
The Stewart Pro Platform model was born out of this iterative development process. This version implemented many hardware and software features which eventually led us to bring our old Stewart Platform design into its final form. So, we no longer separate two products like Stewart Platform and Stewart Pro Platform, as they are the same product now, with the Stewart Platform being a single configuration with short lead times and anything different than its default configuration is the custom version of it.
In the next section, we will provide details of the hardware components.
2) Physical Aspects and Capabilities
The Stewart Platform is designed to deliver accurate results. Every component in the system, from its actuators to its software algorithms, has been fine-tuned to achieve optimal motion control accuracy. The Stewart Platforms precision motion control technology enables it to handle tasks requiring pinpoint accuracy, from delicate instrument testing to carrying substantial loads.
Built-in Motion Control and Kinematics
For the motion control, the firmware is using 3rd and 5th order trajectory generation equations. In order to move the manipulator from its original position to a goal position at a certain rate, we have to solve some mathematical equations for defining the robot’s pose and then calculate motor positions and the trajectory of the robot itself. We will share some information about these calculations.
Set of joint angles is calculated with the help of inverse kinematic dynamics of the manipulator. We have initial and target angles of the manipulator. Similarly, in the cartesian space scheme, we know the initial angles of the motors and the end-effector initial position is also calculated with the help of forward kinematics. The target position is the desired position to move. We benefited from the paper titled “Analysis and Implementation of 6 DOF Stewart Platform-Based Robotic Wrist” 1. The cubic polynomial has the following form:
If the cubic polynomial is derived two times respect to time, we obtain velocity and acceleration of the manipulator:
These are the main equations we are using, for more equations and information you will have guidance with our documentation and videos.
A common question we get is “How can we know / calculate the accessible workspace of the Stewart Platform?”. For an easy answer, the software has a continuous internal check while the platform is working. In case any requested coordinate is out-of-the reach of the robot, the software will return an “Out-of-workspace” message and the requested motion command will not be executed. User should send a “Clear Motion '' command to clear the error message and then can resend a new position command.
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For offline trials, ACROME also provides a Kinematics Calculator simulation program, which mimics the kinematics calculations. Users can play with the knobs/values to see if the requested motion command is within the workspace of their product.
Durability & Robustness
The Stewart Platform is designed to be durable, built with high-quality materials and advanced manufacturing processes. Its sturdy build ensures it can withstand the demands of intensive operations. We have three important components for this statement.
- Heavy-duty industrial linear actuators, with default IP54 ratings and 30,000+ hour life-expectancy under nominal conditions,
- Anodized aluminum base and top plates, that are stiff and scratch resistant,
- Double bearing mechanism to ensure repeatability and precision, achieving sub-millimeter accuracy, making it vital for tasks requiring exact positioning.
The platform's long-lasting reliability is a testament to its high quality.
Modularity & Customization
The modularity of the Stewart Platform is a standout feature. The design of the Stewart Platform allows for adaptability and customization to meet industry-specific needs. It should be noted that the legs, top and bottom plates of the product are field replaceable. Please check our assembly guide video and see how easy it is to assemble and disassemble the product.
This modularity makes the Stewart Platform a highly flexible product, easily configured to meet the unique requirements of different industries.
High Payload vs. High Speed Options
The Stewart Platforms can be used to perform tasks ranging from conducting instrument dynamics tests to transporting bulky weights. Thanks to the modular design, the actuators of the ACROME’s Stewart Platform can be changed to adapt high payload or high-speed applications. So, the Stewart Platform has two options, high-speed and high-payload.
The high-payload option provides precise motion control and makes it an ideal platform for industries that require accurate movement of heavy loads
The high-speed option on the other hand is designed to fulfill various operational motion needs. Its ability to effortlessly switch between slow, precise movements and fast-paced, high-intensity sequences makes it a versatile platform. The combination of speed and responsiveness of the Stewart Platform allows it to handle a wide range of movement dynamics. To check related material, and obtain more information you can see our blog post.
Motion Dynamics
The 6-DOF of the Stewart Platform ensures a wide range of motion that enables it to perform complex movements which are critical for applications requiring intricate motion sequences. The ability of the device to replicate real-world movements, simulate diverse conditions, and execute precise movements makes it a valuable tool for industries ranging from aerospace to entertainment. For more information you can check our case study with FotoKite
3) Deliverables
Shipping Box and its Content
Unless strictly requested, every Stewart Platform shipped by ACROME is first assembled, tested and then disassembled prior to shipment. This method of shipping has multiple advantages such as;
- More protection against shock & vibration during shipment stage
- Smaller shipping box size
- No thread-lockers are required (which is good for replacement) to avoid the unwanted un-screwing due to airfreight conditions
Inside the shipping box (as in the above image), following items are placed from bottom to top:
- Protective foam layer (top, bottom and sides)
- Base and top plates
- Qty.6 leg assembly, which is a pre-assembled unit based on linear actuators, bearings and joints
- Power box with a 110V / 230V compatible power supply inside.
- Motor driver board and the embedded controller of the Stewart Platform
- All necessary connection cables, including 1.5m ethernet cable for connecting to the user’s PC
- USB flash drive which includes the following documentation and the PC software (ie. ACROME Stewart Platform Software). More information on the PC software is provided in the next section.
- Package content document (ie. items that are tested and shipped)
- Assembly Manual
- Getting Started Document with hardware and software installation instructions
- PC Software User Manual
- API documentation for external (ie. custom) programming
Graphical User Interface with User-Centric Design
The Stewart Platform is not solely about technology; it also prioritizes the user experience. The software interface is based on a common and easy to use API (Application Programming Interface). For non-programmers, first time users or initial commissioning purposes ACROME also provides a ready-to-use intuitive graphical user interface (GUI) for Stewart Platform.
The GUI’s controls are ergonomic, and the design is user-friendly. This makes it easy for new robotics users to make use of the Stewart Platform’s capabilities. Users can execute their own motion scenarios by uploading a spreadsheet (ie. MS Excel) file with a .csv extension. To learn more about this, please check our Stewart Platform - Excel Import video . Also user can experiment with vibration modes.
API Document for Easy Integration
Acrome's commitment to making technology accessible is reflected in its user-centric approach. However, we know that in some cases, a custom software solution may be required for integration. The Stewart Platform’s ability to integrate seamlessly with various software and hardware ecosystems ensures that it fits effortlessly into diverse operational setups. Its compatibility with different systems, devices and networks makes it a flexible platform that can be easily adapted to different industrial needs. The API (Application Programming Interface) document is provided by default to all users.
There are video guidelines such as the below one for how to use the commands of the API.
4) Applications: Case Studies and Example Uses Cases
The applications for the Stewart Platform are as diverse as its features. Its versatility, precision and adaptability make it a valuable tool across a wide range of industries. From simulating flight conditions to creating immersive virtual experiences, the Stewart Platform's applications are a testament to its innovation and potential.
Aerospace & Defense
Precision is of utmost importance in the aerospace and defence sectors. The Stewart Platform is an invaluable tool as it can simulate flight conditions, test aerospace components, and carry out training simulations. Its precise motion control, high payload capacity, and wide range of motion enable it to handle the complex and demanding tasks demanded by these industries.
Entertainment & Virtual Reality
The entertainment and virtual reality industries rely on immersion, and the Stewart Platform's capability to replicate real-world motions elevates this experience to an unprecedented degree. The Stewart Platform's motion dynamics, speed, and responsiveness make it a perfect platform for the creation of realistic motion effects in movies as well as the simulation of physical sensations in virtual reality experiences.
Research & Academia
The Stewart Platform hexapod platform is not just an industrial tool, but a versatile platform for exploration and discovery. Researchers and academics worldwide utilize its capabilities for various experiments. The precision, adaptability, and versatility of the platform make it a valuable tool for research and development that allows scientists to push the boundaries of what's possible in robotics. The exceptional modularity and customization options of the Stewart Platform make it a platform that can be tailored to specific needs and requirements, making it an ideal tool for researchers and academics.
References:
[1] Charles C. Nguyen, Sami C. Antrazi, Zhen-Lei Zhou, Charles E. Campbell, Analysis and implementation of a 6 DOF Stewart Platform-based robotic wrist, ISSN 0045-7906.
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