In recent years, research has been conducted on the production of exoskeleton robots. This is mainly due to increased demand in several areas, e.g. B. the medical industry. Due to the different functions of these robotic exoskeletons, there is a large consumer market to meet different needs and uses.
This article presents design considerations for meeting the requirements of exoskeleton robots and analyzes the manufacturing of exoskeleton robot parts. Let's start.
What are exoskeleton robots?
First, let's learn what a robotic exoskeleton is. Exoskeleton robots were originally developed in the 1960s for injured soldiers and have since been used in various types of medical robotics, film effects, and military applications to support and strengthen the human body.
Considering the requirements of these wearable robots in different fields, they are classified into active and passive drive methods. On the one hand, active propulsion methods with exoskeletons use actuators that convert hydraulic, pneumatic or electrical energy into mechanical energy for the user. On the other hand, passive exoskeletons support the user and offer flexible assistance.
For this reason, there is currently a high demand for these versatile exoskeleton robots, especially due to their flexible support, precision and ability to handle different requirements.
How are exoskeleton robots used in medical rehabilitation?
Medical exoskeletons are an important application for rehabilitation robots. These exoskeleton robots typically provide rehabilitation treatments and help patients regain mobility. Nowadays, medical exoskeleton robot manufacturing technologies have made great advances. They provide supportive care to people with injuries and disabilities to help them recover more quickly.
Furthermore, these medical assisted exoskeleton robots are divided into augmentative and rehabilitative types that support people with these wearable mobility aids. The augmentative process helps patients perform tasks efficiently and relieves them of strain. In contrast, rehabilitation exoskeletons, typically used in physical therapy sessions, promote recovery.
Medical exoskeletons can also be divided into upper extremity exoskeletons (shoulders, arms, back) and lower extremity exoskeletons (legs, ankles, feet). In this way, they can be easily used in physiotherapy sessions or at home, helping patients to continue training and reducing the level of support when improvement is observed.
Design Considerations for Robotic Exoskeletons
The production of exoskeleton robots requires ongoing research and consideration in the design and testing phases. Portability, flexibility, adaptability and lightness are key factors in exoskeleton design. Therefore, some important design considerations are taken into account when developing and customizing an exoskeleton robot. Some of them are listed below:
Consider ergonomics
For robotic exoskeletons to work, artificial joints are aligned with human joints. With this in mind, designers must ensure that the range of motion of the artificial joint is consistent with human joints to avoid pain during pressure loads. The full range of human articulation must be guaranteed with minimal mechanical changes. This ensures that the force applied is within the range that human limbs can withstand and ensures an ergonomic design of the exoskeleton.
Power transmission
The human body has complex kinematics, with multiple degrees of freedom (DOF) at each joint. To overcome this, designers are looking for alternative ways of transmitting power and enabling transmission through bond-based mechanical devices. These link-based kinematic chains, made of materials of different hardness, increase the transmission force, reduce the size of the actuator, thus allowing safe and comfortable power transmission.
In rigid robotic exoskeletons, the mechanical structures are aligned with each joint and utilize a direct drive or gear system. This allows the actuators to be mounted close to the structure, making them portable. Soft exoskeletons are made from flexible materials and are shaped like a lightweight glove that transmits force directly to the fingers. Devices powered by tendons, artificial muscles, and flexible, jointless structures are used to transmit force.
Calibration and sizes
Because exoskeleton robots are widespread and not all potential users have the same limb size, some users are at risk of incorrect positioning or improper operation, which may affect rehabilitation treatments. Furthermore, it must be ensured that the use of a robot exoskeleton is painless. Thus, robotic exoskeleton devices require an acceptable adjustment range for different limb sizes.
Therefore, when designing the exoskeleton, it is important that it allows for a maximum range of limb sizes and does not cause secondary injuries to the users. To achieve this, systems such as mechanical stops, force limits or rotation limits must be used to prevent excessive range of motion.
Light materials
To ensure comfortable operation of exoskeletons, it is important that exoskeleton robot parts use lightweight materials that lighten the user's burden and improve portability. Designers must take care to minimize the size and weight of mechanical components.
To this end, soft exoskeletons (made of materials such as silicone) are comfortable due to the absence of “rigid” structures. Furthermore, for rigid materials, a robot with an aluminum exoskeleton is the preferred choice. Due to its light weight and durability, as well as its high resistance to stress, it is a preferred metallic material for mechanical structural elements used in the production of exoskeleton robots.
Rapid production of exoskeleton robots: how does on-demand manufacturing work?
To achieve shorter development cycles, it is important to optimize the manufacturing process of robot exoskeleton components. Below are some processes and methods to ensure exoskeleton robots reach the market quickly.
Flexible design iterations
To meet manufacturing requirements for robotic exoskeletons, it is important to ensure flexible design iterations. This contributes to the accurate and efficient design and manufacturing of exoskeletons, enabling optimization. On-demand manufacturing therefore allows customization, producing prototypes and robotic exoskeleton parts for customers with different needs, ensuring short delivery times.
Fast production
Rapid production with custom machining enables the production of efficient and cost-effective robotic exoskeleton parts, enabling faster time to market. By producing low-cost exoskeleton components, it is easier to capture a larger market of users. This is particularly important for rehabilitation robotic exoskeletons. As there is no minimum order quantity required, faster and more flexible production can be realized.
Simplify the development process
On-demand manufacturing solutions allow you to quickly turn your ideas into reality. They help simplify the development processes for exoskeleton robots. They also contribute significantly to reducing production costs by using fewer resources, making the exoskeleton robot more accessible to consumers. This allows for flexible ordering that meets the user's needs.
Furthermore, on-demand production optimizes product delivery time. Efficiency and productivity are also kept under control, reducing errors and ensuring the delivery of high-quality end products.
Comprehensive editing options
To facilitate on-demand development, rapid production capabilities are deployed that run multiple processes and enable processing in a single location. Using CNC machining robots, 3D printing, sheet metal processing, surface finishing techniques, etc., you can efficiently realize your exoskeleton robot projects from prototype to production. These advanced technologies ensure precision and accuracy in custom exoskeleton parts, ensuring high-quality delivery to the user.
Case Study on Customized Exoskeleton Robotic Parts
The demand for medical exoskeletons for rehabilitation and augmentation purposes is increasing. This includes exoskeletons for upper and lower extremities. Both exoskeleton robots produced consist of several parts, most of which are machined. We would like to present a case about the production of exoskeleton parts for upper limb rehabilitation.
How do the machined parts serve the exoskeleton mechanism?
The shoulder mechanism is an exoskeleton module for upper limb rehabilitation. It is light and compact and ensures maximum range of motion of the human shoulder joint, which in turn drives the rotation of the shoulder joints and makes the shell of the large and small areas of the arm mobile. In this section, we focus on the machining of two typical robot exoskeleton components, namely custom-made exoskeleton stator brackets and housings.
Machined stator assembly
The stator assembly is a fixed and stationary key part in an electric motor. It is used to create a rotating magnetic field when an alternating current passes through it. This induced magnetic field creates a voltage that causes the rotor to rotate.
In this case, the material used to support the stator is AL6061-T6 with light and robust mechanical properties. Precision is important during machining because the stator is integrated with other parts of the exoskeleton. Some concerns when editing this part are listed below:
As the stator is positioned together with other parts, it must be handled with care during machining. When editing, the following three points should be considered carefully.
- (1) As it needs to be positioned and assembled with other parts of the exoskeleton, the size and position tolerance of the 12 holes marked in red in the image are crucial.
- (2) The wall thickness at the point indicated by the red arrow is only 2 mm, and there is a risk of deformation of the stator mounting part due to the pressure of the milling tool during machining.
- (3) The yellow surface comes into contact with a more sensitive part. Therefore, the treated surface must be as smooth as possible. A surface roughness of Ra0.8 must be achieved.
Stator support machining process
We use 3, 4 and 5 axis milling machines to machine these parts.
- First, the front is milled and then the milled hollow structure is filled with plaster. After hardening, the front is milled and returns to its original state.
- We then use a 3-axis machine to mill the back in the same way as the front. After milling, we remove the plaster filled in the first process. This is how we get a double-sided semi-finished product.
- Finally, use the already machined structure to position on a 4 or 5 axis machine, create a feedback device and machine the structures on the 3 sides one by one.
This detailed machining process ensures precise manufacturing of the stator support and meets the requirements of the exoskeleton shoulder mechanism.
Machined Robotic Exoskeleton Housing
The robotic exoskeleton housing is also an important part of the overall design of an upper limb rehabilitation exoskeleton, as it provides a protective and functional covering for complex internal mechanisms. Similar to the precision required for machined stator assembly, the housing requires special attention during the manufacturing process to ensure optimal performance.
Like the stator support, the housing is made from AL6061-T6. When machining shell parts, certain dimensional tolerances must also be taken into consideration to ensure correct alignment and assembly with other exoskeleton components. In particular, those relating to the attachment points and the interface with other modules must be strictly controlled to ensure a precise fit.
Furthermore, maintaining the structural integrity of the case is of utmost importance. Areas with thin walls or complex features require careful machining to avoid deformation or weak points.
Surface Processing for Customized Exoskeleton Robots
Because exoskeleton parts are used repeatedly and case parts are visible to end users, most of these exoskeleton parts require post-treatment to make them aesthetically pleasing and resistant to corrosion. For aluminum exoskeleton parts, sand blasting and subsequent anodizing is the most suitable solution in this case.
Therefore, we first clean all aluminum parts and then sand and anodize them. On the one hand, sandblasting hides processing marks and footmarks and gives the processed exoskeleton parts a matte surface with uniform roughness. On the other hand, anodizing improves the corrosion resistance of aluminum, provides a hard, scratch-resistant surface and improves the appearance of the exoskeleton.
Quality control
To look
Because these exoskeleton components must be suspended in the device during the oxidation process, they will be scratched if you are not careful when removing them. Therefore, parts should be placed at a distance of 20 cm from the eyes during inspection to allow careful inspection. In addition, all parts are assembled on the same robot, and the uniformity and uniformity of the oxidized color of different parts is particularly important. After checking, the appearance and color will be achieved with the desired effect.
Dimensions
Test reports show that we achieved even higher accuracy than necessary.
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