# A Parallel Robot with Torque Monitoring for Brachial Monoparesis Rehabilitation Tasks
## 2 Materials and Methods
### The Development of Torque Monitoring System  
The need to monitor torque during the procedure came as a result of in-hospital tests performed on patients [39; 40; 41; 42], where the ASPIRE succeeded in performing the required rehabilitation motion, but there were times when the operator had to manually stop the robotic system because the patient arm was unable to achieve the desired amplitude due to its spasticity. Figure 8 presents the dynamic control loop of the rehabilitation system. The functioning of the system is based on _Normal Run_ sequence. In _Normal Run_, motion parameters (motion amplitudes, velocity, and number of repetitions) are given using the graphical user interface. Using inverse kinematics, data required for reaching the imposed amplitudes are transferred to the PLC which sends as inputs to the drivers the positions, velocities, accelerations, and a torque limit for the imposed motion (P.V.A.T). The drivers send the data to the motors and in exchange they read the state parameters of each motor (P.V.A.T), and transmit the data to the PLC which provides dynamic feedback to the user. If there are differences between the data imposed via the Normal Run mode and those provided by the dynamic feedback, the system enters another state named _Correction Run_. The _correction run_ is activated when torque monitor system identifies some irregularities in torque variation created by external factors. In this case the system signals the event and requires the physiotherapist interventions in fixing the problem. When _correction run_ is activated, the robotic system identified a disturbing external factor that affects the rehabilitation procedure. Different scenarios are required for this correction run based on the external factor type and the observation of the physiotherapist. After analyzing the risk factors from above, three scenarios have been developed (Figure 8):  
* The first scenario (**Red scenario**) implies spasm seizures or other critical situations that may endanger the patient. In this case the operator must press the emergency button and the patient is detached from the rehabilitation robot and primary care is administrated. The procedure may be resumed when the patient is in stable condition. This scenario is represented with red arrows and red blocks in Figure 9, and the output of this scenario is the end of the rehabilitation procedure due to unplanned events. * The second scenario (**Yellow scenario**) includes reaching a spasticity limit or striving muscular pain. In this case, the system may return to the normal run after reversing direction. The system may re-enter the correction run mode when/if the spasticity limit is reached in the opposite direction. This scenario is represented with yellow arrows and yellow blocks in Figure 9 and the output of this scenario is Normal Run, the system that resumes the rehabilitation procedure until the next event. * The third scenario (**Green scenario**) is related to some non-critical situations (the patient rearranged his position, tremor, etc.). In this case the physiotherapist may resume the normal run. This scenario is represented with green arrows and green blocks in Figure 9, and the output of the scenario is also Normal Run, the system that resumes the rehabilitation motion until the next event. Figure 8: Dynamic control loop (P.V.A.T. = Positions, Velocities, Accelerations, Torque). After developing the torque-monitoring strategy, the hardware architecture of the robotic system was reviewed, and the communication protocol was modified (old system used Virtual Network Connection while the new torque-monitoring system was based on Modbus protocol-required by the programming unit. In addition, the old interface was implemented in the PLC with the obvious limitations regarding graphical quality and extra functions (such as a database and exercise logging). The hardware configuration of the system is presented in Figure 10.  
The components of the robotic system are divided into 3 levels.