## 2 Materials and Methods  
### The Main Components of the CPM Device  
_Research Object Characteristics_  
The design optimisation study will be carried out using Generative Design methods. It will focus on the main positioner of the CPM rehabilitation device. The research object will be a virtual model of the CPM device developed in the SolidWorks 2023 software environment. The main dimensions of the device components were taken from an analysis of design guidelines for this type of biomedical solution, based on an atlas of human measurements and data for ergonomic design and evaluation [34; 35]. The kinematic configuration adopted for the study corresponds to the dimensions of male specimens according to the 95 Centile model. A general view of the developed virtual CPM rehabilitation device model is shown in Figure 1.  
The supporting structure of the CPM unit (1) and the main positioner (2) was based on commercially available 40 \(\times\) 40 mm aluminium structural profiles with a single 10 mm  
Figure 1: View of a virtual model of CPM rehabilitation device: (1) CPM unit; (2) main positioner; (3) crank–slider mechanisms; (4) movable sliding guide; (5) actuator; (6) calf support yoke; (7) support the patient’s feet; (8) electric linear actuators; (9) limb support; (10) elastic straps; (11) control box; (12) seat; (13) height-adjustable backrest. groove. The entire support frame was mainly assembled using mounting brackets and 10 M6 slot nuts. This allows the unit to be assembled according to the instructions supplied, and also makes the unit smaller when folded for transport. The main two-leg positioner system is driven by two separate crank-slider mechanisms (3) driven by an electric actuator coupled to a mechanical gearbox (5). The CPM device is mainly used for rehabilitation of the lower limbs: left and right, synchronous and asynchronous. The control mode of the main lower limb positioner system is selected by the rehabilitation therapist for each patient individually, depending on the rehabilitation needs, both immediately after the procedure and in further stages of kinesitherapy supported by the mechatronic device. The CPM has two independently controlled platforms, mainly used to support the patient's feet (7) during the movement of the main positioners. Structurally, the kinematic chain is formed by a calf support yoke (6), which forms a fixed platform, the aforementioned movable lower foot support platform and three electric linear actuators (8), which are coupled to the platform via rotary joints, thus forming a parallel tripod robot structure. The working position of the mobile platform can be either permanently fixed during the entire movement of the main positioner or dynamically changed during the movement. The movement of the platforms supporting the patient's feet is independent of the movement of the main positioners. This allows the device to be used as a CPM for the ankle, increasing its potential applications. The movable platforms adapt to the current position of the foot, increasing the range of applications, particularly for patients with clubfoot, valgus or spastic feet, characteristic of post-stroke patients, and patients with multiple sclerosis or other neurodegenerative diseases. It is therefore possible to perform passive movement exercises, taking into account the prescribed complex supination and pronation movements, as well as exercises with variable loads--exercises that actively stimulate the muscles. These exercises are usually performed at a later stage in the patient's rehabilitation. The movable links of the main positioner are fixed to the support structure on the patient side and are movable on the other side using a movable sliding guide (4). The main positioner links are responsible for programmable displacement at the knee joint, increasing the value of the ROM and, in the second control mode, with simultaneous passive movement of the foot support plane.