Call For Tenders

The Objective

Millions of patients worldwide suffer from knee joint disorders, including quadriceps weakness, Patellofemoral Pain Syndrome, or from injuries, stroke, post-polio, multiples sclerosis, or SCI. An improvement in lower extremity assistive devices will benefit some or all of these patients. However, with few exceptions, orthotic options for this population are limited to passive technologies that cannot provide the assistance necessary to replicate the function of an unaffected limb. It is estimated an incidence of 2,29 knee injuries per 1.000 population1, most of them requiring a rehabilitation period. In spite of this high incidence, available rehabilitation devices in the market are not fully tailored for an effective and cheap rehabilitation of the gait. Accordingly, there is great potential for the development of Robotic Assisted Rehabilitation (RAR) devices to drastically increase the quality of life of this population.

During 2018, the company GOGOA (, specialized in design, manufacturing, and commercialization of Robotic Assisted Rehabilitation (RAR) systems, has developed a first prototype of the BELK system, a wearable robotic device that can be used for knee rehabilitation, in the sub-acute phase of knee injuries. As BELK is a wearable device, it can be used both, by the physiotherapist in the rehabilitation centers, improving the knee rehabilitation process and increasing patients’ comfort, and by the patients themselves (at home or even on the street), helping them in their usual activities while, at the same time, accelerating their rehabilitation process.

The objective of this CALL FOR TENDERS is to select the best offer for subcontracting exhaustive clinical studies and validation of BELK to a reference rehabilitation institution (public or private hospital) under real-life conditions, defining the clinical protocols and showing its advantages in the rehabilitation process of patients. This activity is part of the EU-funded project ‘Wearable exoskeleton for knee rehabilitation with Functional Electrical Stimulation — BELK’ (Grant Agreement 829620), within the H2020- EIC-SME Instrument Phase II Program (


1 Epidemiology of 6.6 million knee injuries presenting to United States emergency departments. Gage BE, McIlvain NM, Collins CL, Fields SK, Comstock RD.


Main Characteristics of the Belk System

BELK is a powered wearable robotic knee rehabilitation device, integrated with a FES (Functional Electrical Stimulation) system, that present advanced features over existing competing technologies (mainly CPM – Continuous Passive Motion – or powered KAFO – Knee Ankle Foot Orthosis – devices) for knee rehabilitation.

Main elements constituting the BELK system are:

  • Knee Actuator: Brushless motor + Cable transmission2 system. This transmission (patented) gives in the knee a nominal torque of 24 Nm., one of the highest torques in commercial devices, and allows to reduce significantly the costs, compared with the transmission using a planetary gear, common in robotic devices.

  • Power supply: Li-ion battery, 22,5 Volts, and 4 Ah capacity. This battery supplies autonomy of 4 hours at normal working conditions.

  • Sensors: 1 absolute encoder, 3 Hall effect sensors and 4 strain gauges determine parameters such as angular position and velocity, force and interaction torque between user’s limb and the BELK system. 

  • Main controller: The main controller is based on a customized electronic board designed specifically for real-time control of the system.

  • Control algorithm for gait assistance: This algorithm takes into account the interaction torque between the patient and BELK, in order to produce an adaptive reference for gait assistance. 

  • Algorithm for FES integration: Functional electrical stimulation (FES) applies small electrical pulses to paralyzed muscles to restore or improve their function. The combination of an exoskeleton and FES allows a more efficient and personalized rehabilitation. This intelligent algorithm adapts the amount of muscular activation needed at each moment depending on the patient (muscular performance) through FES and the impedance of the exoskeleton at that particular moment.

What has not been properly resolved in practice, and where GOGOA has detected a great market opportunity is in mechatronics systems to aid rehabilitation in the Functional Training phase. In this phase the patient is already able to walk, and therefore needs a system that accompanies him/her, and that actively helps him/her to recover all the functionality of the knee. Therefore, BELK is a wearable system that assists when and where the patient needs it intelligently through proper control of the system and optimized gait assistance techniques not applied by their competitors to date:

  • First, there is a powered and wearable solution allowing users to perform knee rehabilitation during normal walking, unlike CPM devices. Through a careful design it has been achieved an active knee orthosis that allows patients to rehabilitate the knee while walking. It is a one-joint-exoskeleton with an innovative transmission system (cable transmission – patented) that make possible to produce it at a reduced cost, which implies a final price similar to this one of CPM devices, but offering very advanced functionalities over them.

  • Second, it is about providing the patient with "only when you need it" assistance, when currently the existing powered KAFO devices offer assistance based on all or nothing assistance. Current CPM systems are dedicated exclusively to repeat the movements that a physiotherapist would perform in a session, while KAFO devices reproduce a “robotic” movement, with very rigid pattern of movement, due to the lack of real-time adjustment between the force that patient can do and the force applied by the driver. BELK system only helps the movement in the stretch where the patient cannot. If the patient can perform half of the movement, the system will assist him/her only in the other half. This implies intentionality by the patient that allows accelerating the rehabilitation since the effort realized is superior. 

  • Third, GOGOA has developed an algorithm to integrate Functional Electric Stimulation (FES) capabilities with the BELK robotic device. This intelligent and adaptable control algorithm allows to modulate the mechanical impedance that the exoskeleton exerts on the leg, combining the individual pattern of motion of the patient, the position of the leg and the force of the interaction between the patient and the device. In this way BELK offers a variable resistance to the movement of the leg depending on what is needed at each moment. Therefore, inducing variable muscle activation in the leg, which is indicated for optimal rehabilitation. None of the commercial knee rehabilitation devices (CPM, KAFO or exoskeletons) have this possibility. 

Assisted-as-needed control allows to create a force field along a desired trajectory, proportionally applying torque only when patient deviates from the pre-programmed correct pattern. This force field control, by assisting only the segments that the patient need, produces a natural gait pattern, improving the rehabilitation process. Moreover, integration with muscular electrical stimulation (FES) accelerates this process. The algorithm we have developed commands simultaneously the assist as needed loop (force, speed and position) of the BELK device and the Functional Electro Stimulation array of electrodes to induce the muscles contraction – extension in each knee movement coordinated in real time. This innovation makes knee rehabilitation process more efficient and effective, activating muscles and generating controlled knee gait obtaining better rehabilitation in less time.

In addition, the system is designed to be used at home, with no need to go to the rehabilitation centre, saving money and time, as well as the patient's mood. 


2 Some of the advantages of this type of transmissions: (i) No slackness (ii) Low friction (iii) High accuracy (iv) Softness of operation (v) High rigidity (vi) Low cost (vii) High performance (viii) Virtually maintenance-free (ix) Benefits invariant with use (x) Lubrication is not needed (xi) Suitable for low and high loads (xii) Silent (xiii) Can work underwater (xiv) Clean for use in demanding environments


The Clinical Tests To Be Done

Activities to be performed by the selected clinical institution includes:

  • Full definition of the inclusion / exclusion criteria: Objective of the task would be to focus within the general population of subject with gait disorders that may benefit from BELK therapy the groups of end-users that will be considered to evaluate the system. This is more so when dealing with neurological patient in which motor disabilities may be associated with cognitive impairments. According to this purpose, related inclusion / exclusion criteria will be set.

  • Definition of testing protocols and evaluation metrics: These protocols will be for the functional and clinical validation. It must be performed the identification and selection of neurological and functional assessment scales, with particular attention to the gait and related daily life activities.

  • Clinical trials: Aim of this task is to prove the functional and clinical applicability of BELK on the rehab process. To this end is must be identified a set of tools (scales, questionnaires and quantitative indexes) to evaluate all the aspects related to the impact of the use of the device on the quality of life and of the patients. Therefore, a clinical study in which data collected from patients whose treatment will be planned with BELK will be compared to data from controls underwent a classical physical therapy. The study design will be a crossover longitudinal study. Also, the users’ (patients and professionals) satisfaction will be measured (use of the exoskeleton without professional help, perception of the increase in mobility, improvement of the sensibility/proprioception in the affected leg, interest for using the device, fatigue after the training session, etc.). 



  • Deadline for submission of tenders: 31 May 2019

  • Selection of the clinical institution and communication of the results of this call for tenders: 10 June 2019.

  • Start of preparation of the clinical trials: 15 June 2019. 

  • Training by GOGOA of the clinical personnel: September 2019.

  • Deadline for finalisation of the clinical trials: 30 September 2020.

  • Edition of the final report with the results obtained in the clinical trials: 15 October 2020.


Expected Content of the Tender

  1. Short profile of the clinical institution. 

  2. Short CV of the key team personal of the rehabilitation services. 

  3. Existing facilities for rehabilitation and experience using robotic rehabilitation devices. 

  4. Previous experience in performing clinical trials 

  5. Previous experience in EU-funded projects. 

  6. Preliminary definition of the experimentation protocols and metrics to be used 

  7. Preliminary definition of the work plan

Suggested size for this information is a maximum of 15 pages


Criteria for Tenders Evaluation

  1. Experience and qualification of the clinical institution and the rehabilitation team.

  2. Expected number of patients involved in the experiment.

  3. Preliminary definition of the experimentation protocols and planning.

  4. Experience in performing clinical trials.

  5. Previous participation in EU-funded projects.

  6. Price.



Questions about this call for tenders and tenders must be submitted by e-mail to the following address:


©2019 by belk.