## 5 Discussion  
This research shows that the ASMVA controller is more suitable for patients with residual muscle strength of lower limbs than the fixed parameter admittance controller, because the ASMVA controller can estimate the patient's active joint torque according to the human-exoskeleton interaction force, so as to obtain the patient's movement intention. It can not only increase the training intensity according to the active muscle strength of the patient during the patient's active movement intention to increase the patient's active participation, but also increase the trajectory adjustment amount during the patient's negative movement intention to ensure patient's safety. The present study differs from other studies in two main aspects. Firstly, this paper proposes an innovative method to estimate the active joint torque of the exoskeleton wearer based on the standard human-exoskeleton interaction torque. Secondly, the ASMVA controller is introduced into the control of the lower limb rehabilitation exoskeleton robot, which realizes the exoskeleton admittance control with the change of admittance parameters. Unlike the previous research [34; 35], in our study, the input of admittance controller is the active joint torque of patients, rather than the interaction between the exoskeleton and patients' limbs. Ee used the variable admittance controller, which can adaptively adjust the admittance parameters according to the patient's movement intention during rehabilitation training. The biggest advantage of our research is that our study took into account the patients' positive and negative movement intentions during rehabilitation training, which realizes the control of the exoskeleton based on the patient's movement intention, so as to improve efficiency of the training. When the patient has positive intention in rehabilitation training, increasing admittance parameters means increasing the stiffness and damping of the system; then, the intensity of rehabilitation training is increased to ensure participation of the patients. When the patient has negative intention in rehabilitation training, decreasing admittance parameters means decrease the stiffness and damping of the system, which can ensure the safety and comfort of the patient. Clinical research has confirmed that the lack of muscle strength in patients with dyskinesia is an important factor affecting the recovery of limb function [36], and the lack of muscle strength has a direct responsibility in causing sports reinjury [37]. Therefore, in rehabilitation training, it is very important to improve muscle strength of the lower limbs of patients. Research by [PERSON] et al. [38] confirmed that improving the participation of patients in the process of rehabilitation training is very helpful in improving the muscle strength of patients. As an example, for patients with locomotive syndrome and sarcopenia, their affected limbs retain a certain of muscle strength. At this time, the ASMVA controller can be applied to the rehabilitation training of this kind of patients, because the ASMVA controller can estimate the active joint torque of the lower limbs of the patients, so as to judge the movement intention of the patients to adjust the rehabilitation training trajectory adaptively. The ASMVA controller can adaptively change the intensity of rehabilitation training by judging the positive movement intention of patients and the strength of muscles, so as to ensure the active participation of patients during the rehabilitation training. Besides, the ASMVA also provides a security mechanism, that is, when the controller detects that the direction of the patient's active joint torque is not the same as that of exoskeleton joint velocity, it reduces the admittance parameters to decrease the system stiffness, thus reducing the interaction between the patient and the exoskeleton, and ensuring the safety of patients during the rehabilitation training. Finally, it should be noted that the study had one limitation.