US20170095695A1

US20170095695A1 - Actively Controlled Exercise Device

Info

Publication number: US20170095695A1
Application number: US15/285,990
Authority: US
Inventors: Lee Mangusson; Douglas Johnston; Andrew Metzger
Original assignee: Motive Mechatronics Inc
Current assignee: Motive Mechatronics Inc
Priority date: 2015-10-05
Filing date: 2016-10-05
Publication date: 2017-04-06
Also published as: WO2017062462A1

Abstract

An actively controlled exercise device provides a dynamic force responsive workout. The device includes: a user output arm movably attached to a base frame; an actuator attached between the user output arm and the base frame, the actuator including a motor and an output shaft connected to the user output arm; at least one position sensor attached to the actively controlled exercise device adjacent to the user output arm for detecting a position and velocity of the output arm; a load cell attached to the actively controlled exercise device adjacent to the actuator for detecting a force exerted on the user output arm; and a force controller in communication with the position sensor, the load cell, and the actuator for activating the actuator to impart a force on the user output arm during an exercise repetition.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent Application Ser. No. 62/237,162 for “A System for Actively Controlled Exercise Equipment” to Lee Magnusson et al. and filed on Oct. 5, 2015, the contents of which are incorporated herein by reference in its entirety.

FIELD

This disclosure relates to the field of fitness devices. More particularly, this disclosure relates to a fitness device and system for providing a dynamically adjusted force for optimizing a workout and for collecting, storing, and transmitting data related to activity of the device.

BACKGROUND

Strength training and exercise are old and established institutions. However, significant new wisdom on tools, techniques, and training continue to evolve on a continuing basis. More knowledge of how muscle, connective tissue and joints operate is available now than ever. Numerous theories are available on how strength is improved and how to prevent injury. There is a significant opportunity to combine this knowledge with improved exercise technology to achieve goals faster, safer, and more efficiently.
The problem of building strength requires a versatile approach. Building strength is a non-linear process that is dependent on the person, their muscle, their history, and their current state. Fixed weight or fixed force exercises often provide short term increases but most people will quickly plateau, or level off with their training.
Traditional strength training machines do not provide an effective, safe, and efficient workout for a number of reasons. First, because of friction in the system, the eccentric phase of the workout is at a force lower than the concentric phase. Second, the chance of injury on a weight machine can be high due to the large, instantaneous forces that may be exerted onto human joints. These forces can lead to short term muscle and tendon injury, and long term joint problems. Finally, using a gravity influenced mass to create force adds considerable bulk and weight to the design of a machine.
What is needed, therefore, is a fitness device and system for providing a dynamically adjusted force for optimizing a workout and for collecting, storing, and transmitting data related to activity of the device.

SUMMARY

The above and other needs are met by a force controlled exercise device. In a first aspect, an actively controlled exercise device is provided having: a user output arm movably attached to a base frame and movable in at least a first exercise direction and a second exercise direction, wherein the first exercise direction corresponds to concentric work of a muscle of the user and the second exercise direction corresponds to eccentric work of the muscle of the user; an actuator attached between the user output arm and the base frame, the actuator including a motor and an output shaft connected to the user output arm; at least one position sensor attached to the actively controlled exercise device adjacent to the user output arm for detecting a position and velocity of the output arm; a load cell attached to the actively controlled exercise device adjacent to the actuator for detecting a force exerted on the user output arm; and a force controller in communication with the position sensor, the load cell, and the actuator for receiving data from the at least one sensor attached on the actively controlled exercise device and, in response to position, velocity, and force data received from the position sensor and load cell, activating the actuator to impart a force on the user output arm during an exercise repetition.
In one embodiment, the actuator is a linear actuator. In another embodiment, the actuator is a ball screw linear actuator.
In yet another embodiment, the exercise device further includes both at least one encoder sensor and one force sensor, wherein the force controller activates the actuator based on data detected by both the force sensor and encoder sensor.
In one embodiment, the position sensor is an absolute position encoder.
In another embodiment, the force controller instructs the actuator to impart a force in the second eccentric work direction that is greater than the force imparted on the first concentric work direction.
In yet another embodiment, the force controller activates the actuator to impart a ramped force on the user output arm such that the force is at a minimum when velocity is detected as zero and gradually increases when velocity is detected as being greater or less than zero.
In one embodiment, the force controller activates the actuator to impart a positive force when the position sensor detects the user output arm to be at a first position, and wherein the force controller activates the actuator to impart a negative force when the position sensor detects the user output arm to be at a second position.
In another embodiment, the force controller activates the actuator to move the user control arm along a fixed position and time path, and wherein data related to a force of the user on the user control arm is detected by the load cell adjacent to the actuator.
In one embodiment, the force controller imparts a short perturbance force on the actuator during an exercise and detects a position and velocity response of the user through the user output arm.
In a second aspect, an actively controlled exercise device is provided having: a user output arm movably attached to a base frame and movable in at least a first exercise direction and a second exercise direction, wherein the first exercise direction corresponds to concentric work of a muscle of the user and the second exercise direction corresponds to eccentric work of the muscle of the user; an actuator attached between the user output arm and the base frame, the actuator including a motor and an output shaft connected to the user output arm; at least one position sensor attached to the actively controlled exercise device adjacent to the user output arm for detecting a position and velocity of the output arm; a load cell attached to the actively controlled exercise device adjacent to the actuator for detecting a force exerted on the user output arm; and a force controller comprising a processor and computer readable storage and in electronic communication with the actuator, position sensor, and load cell, the force controller including one or more instructions executable on the processor for detecting position, velocity, and force data from the position sensor and load cell, in response to detected position, velocity, and force data, activating the actuator to impart a force on the user control arm, and adjusting a force imparted on the user control arm based on one of a detected position, force, and velocity of the user control arm.
In a third aspect, a method of actively controlling an exercise device is provided, the method including the steps of: providing a user output arm movable in relation to a base frame; providing at least one encoder sensor and force sensor in communication with the user output arm for detecting a position and velocity of the user output arm and a force imparted on the user output arm; providing an actuator in mechanical communication with the user output arm; providing a force controller in electrical communication with the encoder sensor, force sensor, and actuator; detecting a position and velocity of the user output arm with the encoder sensor; detecting a force exerted on the user output arm by a user with the force sensor; activating the actuator to impart a force on the user control arm based on a detected position, velocity, and force of the user control arm, wherein the force is greater when the user control arm is determined to be moving in an eccentric work direction and less when the user control arm is determined to be moving in a concentric work direction.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, aspects, and advantages of the present disclosure will become better understood by reference to the following detailed description, appended claims, and accompanying figures, wherein elements are not to scale so as to more clearly show the details, wherein like reference numbers indicate like elements throughout the several views, and wherein:

FIGS. 1 and 2 show a controlled exercise machine according to one embodiment of the present disclosure;

FIG. 3 shows a cross-sectional side view of a ball screw actuator according to one embodiment of the present disclosure;

FIG. 4 shows a diagram of operation of a controlled exercise machine according to one embodiment of the present disclosure;

FIG. 5 shows a diagram of workout force applied on a traditional workout machine according to one embodiment of the present disclosure;

FIG. 6 shows a force velocity diagram of an eccentric workout routine according to one embodiment of the present disclosure;

FIGS. 7 and 8 show diagrams of eccentric workout routines having ramped forces according to one embodiment of the present disclosure;

FIG. 9 shows a diagram of a position-time profile of a workout routine according to one embodiment of the present disclosure;

FIG. 10 shows a force and position profile of a workout routine using anti hysteresis control according to one embodiment of the present disclosure;

FIG. 11 shows a force and position profile of a workout routine using anti hysteresis control according to one embodiment of the present disclosure;

FIGS. 12 and 13 show diagrams of the Hill Model of muscle according to one embodiment of the present disclosure;

FIG. 14 shows a diagram of the Hill Model of muscle plotted as a surface with respect to position and velocity;

FIG. 15 shows an example of muscle model control for keeping a user within a specific range of position and velocity according to one embodiment of the present disclosure;

FIG. 16 shows a target region of muscle control according to one embodiment of the present disclosure;

FIG. 17 shows a schematic of weight bounce during an exercise according to one embodiment of the present disclosure;

FIG. 18 shows a position versus time plot of an exercise by a user during a bounce movement according to one embodiment of the present disclosure;

FIG. 19 shows a diagram of a force due to weight bounce and position trajectory according to one embodiment of the present disclosure;

FIG. 20 shows a flat loading force according to one embodiment of the present disclosure;

FIG. 21 shows an example of a variable inertia control according to one embodiment of the present disclosure;

FIG. 22 shows a diagram of a resulting reduced impact force of an exercise with inertia scaling according to one embodiment of the present disclosure; and

FIGS. 23-26 show diagrams of applying perturbations in force during an exercise according to one embodiment of the present disclosure.

DETAILED DESCRIPTION

Various terms used herein are intended to have particular meanings. Some of these terms are defined below for the purpose of clarity. The definitions given below are meant to cover all forms of the words being defined (e.g., singular, plural, present tense, past tense). If the definition of any term below diverges from the commonly understood and/or dictionary definition of such term, the definitions below control.
A system for actively controlling a machine assisted workout is provided that addresses many deficiencies in traditional strength training machines. The system for actively controlling a machine assisted workout improves both strength training and recovery from an injury by providing actively controlled adaptable and customizable loads, highly variable loads that encourage strength through muscle confusion, improved safety, and motivation of a user.
FIG. 1 shows a basic embodiment of an actively controlled exercise machine 10 for strength training or rehabilitation. The actively controlled exercise machine 10 includes a user output arm 12, a base frame 14, an actuator 16, a force sensor 18, and an encoder 20. The actively controlled exercise machine 10 provides a dynamically controlled force matching a twitch force of a user's muscle. By matching force in the manner described herein, an exertion experienced by a user may be linearized thereby resulting in more even distribution of force over the total length of contraction (concentric stage) and relaxation (eccentric stage) of the muscle. A force controller in communication with the actuator, force sensor, and encoder provides controlled real-time feedback to a user for a force controlled workout. The actively controlled exercise machine 10 adaptively responds to muscle exertion of the user to decrease muscle and joint strain of the user typically caused by high, short term loads. By adaptively responding to force generated by user that would cause a high load on muscle and joints, the high instantaneous load can be spread over a longer period of time, and reducing the peak load. Reducing the peak load reduces the stretch rate of the viscoelastic muscle.
Referring to FIGS. 1 and 2, the user output arm 12 is shaped to engage an appendage of a user during an exercise. The user output arm 12 includes a pair of grips 22A and 22B extending from arm bars 24A and 24B. Padding such as a rubber or foam layer formed over the grips 22A and 22B may be included to enhance a grip of a user on the grips 22A and 22B. Grips 22A and 22B may be adjustable attached to the arm bars 24A and 24B to allow a user to adjust a position of the grips 22A and 22B relative to the user. For example, the grips 22A and 22B may be threadably engaged with one or more bores 25 formed through the arm bars 24A and 24B. The arm bars 24A and 24B are attached with a cross-member 26 extending between the arm bars 24A and 24B such that the user output arm 12 is substantially U-shaped.
The above described orientation of the user output arm 12 is configured for a bench-press type workout of a user, wherein the user engages the grips 22A and 22B to push the user output arm away from the user during concentric work of the user's chest and supporting muscles and to resist return of the user output arm 12 towards the user during eccentric work of the user's chest and supporting muscles. While the above description is suitable for bench-press exercises, it is also understood that the user output arm 12 may be formed into a configuration suitable for other types of workouts. For example, the user output arm 12 may include one or more pads or other like portions for contacting legs or other appendages of the user during leg exercises. Such configurations are known and may be readily adapted to the actively controlled exercise machine 10 of the present disclosure.
The base frame 14 includes one or more structural members 28 for supporting a seat 30 and backrest 32. One or more leveling feet 34 are also attached to the structural members 28 for stabilizing the controlled exercise machine 10 on a floor surface. An enclosure 36 may be formed along one of the structural members 28 for supporting and containing a force controller of the controlled exercise machine 10 discussed in greater detail below. The structural members 28 may be formed of a metal, such as steel or aluminum, and may have a rounded or rectangular cross-sectional area.
With further reference to FIGS. 1 and 2, the user output arm 12 is movably attached to the one or more structural members 28 such that the user output arm 12 is supported by the structural members 28 and movable in relation to the structural members 28 during a user exercise. The user output arm 12 may be pivotally attached to one of the structural members 28 such that when a user engages the grips 22A and 22B of the user output arm 12, the user output arm 12 moves in relation to the structural members 28.
The encoder 20 is attached to the controlled exercise machine 10 between the structural members 28 and the user output arm 12 such that the encoder 20 detects a position of the user output arm 12 relative to the stationary base frame 14. The encoder is preferably an absolute position encoder, however it is also understood that various other position sensors may be used to capture data relative to a position of the user output arm 12. The encoder provides absolute position data of the output arm 12 and further provides a velocity of the output arm 12 based on changes in position of the output arm over a given time.
The actuator 16 is attached to the controlled exercise machine 10 between the user output arm 12 and the stationary base frame 14. Referring to FIG. 3, the actuator 16 is preferably a ball screw linear actuator having a mounting bracket 38, a housing 40, a motor core 41 and motor 42 supported on a rotor bearing 43 within the housing 40, and a ball screw shaft 44 located at least partially within and extending from the housing 40. A ball nut 46 engages the ball screw shaft 44 and is supported by a thrust bearing 48. A housing cap 50 is placed on an end of the housing 40 and includes an aperture 52 to allow the ball screw shaft 44 to extend through the housing cap 50. The motor 42 engages the ball nut 46 to rotate the ball nut 46 and thereby cause the ball screw shaft 44 to either extend or retract from the housing 40. A position encoder 53 detects a position of the actuator 16.
The actuator is attached at the mounting bracket 38 to the structural members 28 and at an end of the ball screw shaft 44 to the user output arm. The force sensor 18 preferably comprises a load cell located between the housing and the mounting bracket 38 for detecting a force between the actuator 16 and the user output arm 12. While the figures illustrate the force sensor 18 being located adjacent to the housing 40 of the actuator 16, it is also understood that the force sensor 18 may be located in various other positions such that the force sensor 18 may detect a force between the user output arm 12 and the actuator 16. For example, the force sensor 18 may be located within hand grips 22A and 22B, or adjacent to a point at which the user output arm 12 is attached to the base frame 14.
Referring again to FIG. 1, the controlled exercise machine 10 includes a force controller 58 that is in electronic communication with the actuator 16, the force sensor 18, and the encoder 20 for controlling an activation of the actuator based on data received from the force sensor 18 and encoder 20. The force controller 58 includes a processor and a computer readable storage mediums. Further, executable instructions may be stored on the computer readable storage medium and executed by the processor to activate the actuator in response to a force or position of the user output arm 12 as discussed in greater detail below. The force controller 58 may activate and adjust a force of the actuator based on detected user input and a force of the user's muscles on the user output arm 12 to provide a dynamic exercise that is in response to force imparted on the controlled exercise machine 10 by the user.

Actively Controlled Strength Training

The problem of building strength requires a versatile approach. Building strength is a non-linear process that is dependent on the person, their muscle, their history, and their current state. Fixed weight or fixed force exercises often provide short term increases but most people will quickly plateau, or level off with their training. An actively controlled machine using force and position feedback provides for much greater versatility and matching to an individual's needs. Effective strategies of strength training are available using the controlled exercise device 10 disclosed herein. As shown in FIG. 4, the controlled exercise device 10 is controlled based on an interaction of a mechanical linkage of the device that is controlled by the actuator 16. The actuator 16 is controlled by the force controller, which receives feedback from sensors throughout the system to guide characteristics of the device. System data may be transmitted to a centralized data store.

Intra-Rep Control

Within a single repetition, various effective workouts are available for strength training using the controlled exercise device 10. It is widely reported that muscle is strengthened mostly during eccentric work and not during concentric work or isometric exercise. Eccentric work is the portion of a lifting cycle in which the weight is lowered as the muscle is lengthened. Concentric work is the opposite, the shortening of the muscle and positive work portion of a lifting cycle. Isometric exercise refers to holding a fixed force or weight at constant position. Physical trainers will often recommend eccentric work as a means of strengthening for recovering from an injury. For example, a recommended Achilles Tendinitis recovery exercise is to do calf raises, using both calves to lift the body but a single calf to lower. This gives double the amount of eccentric work applied to the muscle as concentric work. Mostly all standard free-weight based exercises are designed to provide equal concentric and eccentric work. Weight machines in fact produce less eccentric work than concentric work due to friction of their transmissions. This is illustrated by the force-velocity profile in FIG. 5. The actively controlled weight machine however is designed to be infinitely variable and it can provide a force-velocity profile typical of strength building calf workout described above.
One control strategy is to switch between levels of force depending on velocity, wherein a negative velocity represents eccentric work and a positive velocity represents concentric work.
$F = {\begin{matrix} F_{e} & if v \geq 0 \\ F_{e} & if v < 0 \end{matrix}$
This is shown graphically in FIG. 6. It is easy to extend this style of control to include a ramped change in force near zero velocity as shown in FIGS. 7 and 8. This helps make for a less abrupt transition for the user and also helps to improve stability and reduce chatter around zero. It is also relevant to note here that this force vs velocity profile could take any shape as may be desired for the workout. A few more examples are decreasing force with speed to help prevent the user from going too fast. A target velocity range in which force may be provided that is either higher or lower than normal to target specific muscles. Alternatively, a user could program to match a certain muscle model as described further herein.
Using active control, forces may be designated in specific regions of position, velocity, or acceleration. So a training strategy could be to set force levels to target specific regions. In one mode of control, a position vs force ramp is used when changing force levels to help maintain stability and provide a smoother user experience. When direction changes in the positive direction force ramps to lower level and when direction changes is the negative direction force ramps to a higher level, using position as the control variable for the ramp. The ramp could take any shape, such as sigmoidal. An example anti-hysteresis control is shown below using Python code:


	def force_hysteresis (pos,step,fc,fe) :
	ftmp = -step*(pos-force_hysteresis.pos_last) + \
	force_hysteresis.f_last fdes = min(max(ftmp,fc),fe)
	force_hysteresis.f_last = fdes force_hysteresis.pos_last = pos
	return(fdes)
	force_hysteresis.pos_last = 0 force_hysteresis.f_last = 0 step = 1./.4 #
	force per position
	F_hyst = zeros (shape(t)) for i,p in enumerate(pos):
	F_hyst[i] = force_hysteresis(p,step,fc,fe)

Resulting plots for a specific example using this control are shown in FIGS. 9-11.

Other methods of applying eccentric force may be further defined, such as time based control wherein the force controller switches force levels at designated times to encourage a particular cadence and position threshold wherein the force controller will activate the actuator to maintain the user output arm in a certain spatial position in response to user force. Changes in force may be according to a time-based force ramp or other methods of smoothly changing a force of the actuator.
In one mode, the force controller may activate the actuator to maintain a fixed position versus time profile. This profile could be any shape. The user would try to apply maximum effort in both eccentric and concentric directions. Resulting force vs time, averages and other parameters would be displayed to the user and logged for further information. This would provide useful information for fitness evaluation of a user. Further, applying various positions and speed could be used to identify parameters for a target muscle of a user. The parameters may be presented in various forms, such as by providing maximum power or force expected for a designated number of repetitions. Differences between users muscles and standard models may be identified such that routines performed on the controlled exercise machine 10 may target deficient areas.
In another mode of operation, the controlled exercise machine may provide muscle model control workouts. It is known that muscle has a force-position-velocity relationship. This relationship depends on many factors including the type of muscle, its condition, genetics, and is likely specific on a per person basis. In general terms the Hill Muscle Model does a good job explaining the phenomenon seen with muscle, though many other models are available and could be used in our control strategy. An ideal exercise for a muscle would be to apply forces proportional to the muscle's ability at any given time, position, and velocity. It so happens that the muscle model predicts that force ability is much greater in the negative velocity region, so this form of control would likely include eccentric style workouts as described above.
The Hill Muscle Model looks at both active and passive force as a function of position and velocity. Active force is produced by the contractile elements and passive force is due to muscle stretch. The Hill Muscle Model predicts that force has an inverse parabolic relationship as a function of position. The model also predicts low passive force until a threshold distance and then an increase in passive force with position. These two relationships are plotted in FIG. 12. In addition, the Hill Model predicts force as a function of velocity as well. This equation is given as follows:
(v+b)(F+a)=b(F ₀ +a)
where a and b are parameters that fit to a specific muscle. This equation is plotted in FIG. 13.
Next both the position dependence and the velocity dependence of force can be plotted on a single 2 d plot as shown in FIG. 14. A multiplicative contribution of the two contributions was assumed here, but more general models need not make that assumption. Now our muscle model control can measure both position and velocity and apply a force proportional to the values of the model at those position and velocity values. This will provide for a very effective loading of the muscle as well as a natural eccentric workout. Other interesting workouts include using the muscle model but targeting specific regions as shown with examples in FIGS. 15 and 16. As illustrated in FIG. 12, the region is defined as 0.5<v<0.3 and 0.3<p<0.1. In the positive velocity region high force is applied outside the target region, which pushes the user back into the target region. In the negative velocity region, 0 force is applied outside the target region, which signals the user that they have gone outside the target region (note that applying high force here as with positive velocity would end up pulling the user farther from the target). The boundaries in these examples are sharp and dramatic but could also be smooth and less pronounced. Information about the user's position in the model space and in the regions could also be provided through the graphical user interface, sound, and/or haptic feedback.
In addition to the model itself which relates force to muscle length, appropriate corrections may also be applied to map from muscle length to limb position, and for the applicable moment arms of the muscle with respect to the joint center of rotation. Values could be presented to the user and analyzed/controlled in any space (muscle length space, joint angle space, or task space).
The muscle model can also be used in other ways. By applying a trajectory in position control mode as described above, the user's force can be measured. This trajectory could traverse the space of position and velocity such that an accurate muscle model could be created for the specific user. This model could either be a direct map with interpolated values between directly measured values, or it could be used to fit parameters for standard models to the user. The muscle model could also be created simply by applying any type of control and tracking the measured responses from the user. The model could be kept up to date with every workout as well and used as a means for tracking progress over time.
There are several other suitable muscle models in existence. Any of them is relevant for applying control as described above. One other class of key importance is muscle fatigue models. These relate force output vs time and previous history. Models of this sort will be beneficial to adjust the force applied as a function of reps. A decrease in force with reps is sometimes referred to as “tapering.” A model could help predict optimal tapering, but may also be used to change and track the routine in other ways as well. In addition, a model of this sort could be used to track the user during their workout and/or between workouts to dynamically update the workout.
In order to provide a realistic feel for the user it may be beneficial for the actively controlled force to simulate a virtual inertia. This would be given by setting a control force as follows:
F _a =m _v *{umlaut over (x)}
The virtual inertia could be positive, zero, or negative, or a function of other variables such as position, velocity, and time. Negative inertia control provides an interesting exercise which targets stability producing muscles.
The controlled exercise machine 10 of the present disclosure may further assist in impact reduction control. It is well known that people tend to bounce weights and/or use momentum during exercise. Examples include swinging a weight up during a curl exercise or allowing a weight to increase in velocity during the eccentric phase of a bench press, then allowing the weight to bounce off the passive elasticity in the muscle which helps with the concentric phase. These techniques cause a variety of problems. They can reduce the effectiveness of the workout by reducing the load placed on the muscle in key areas, they can cause the recruiting of muscles other than the target muscles, they can increase the impact loading applied to tendons and joints as described below, they can be more dangerous due to the dynamic balance required, and they can simply look uncool at the gym. With an actively controlled force machine these impact forces can be reduced or removed through a variety of different control techniques. An example is provided here. A typical weight bounce is shown schematically in FIG. 17. Any example of the position vs time seen during a bounce is shown in FIG. 18. This trajectory created by the inertia and the user inputs then creates a force, which is shown in FIG. 19. Note that the high peaks are due to the impact on the muscle. The lower peaks occur when the mass is up. There is a decrease in force as the weight is accelerated in the downward direction. So not only does this movement cause high impact forces which can cause injury, it also reduces the load on the user during raising and lowering the weight, which reduces the exercises effectiveness. One method for preventing the inertial bounce completely is to have the force controller actively control a force only without simulate inertia. By controlling force directly, the result would be a perfect constant force as shown in FIG. 20. The user may prefer not to have zero inertia for reasons of stability and feel. In this case one technique we could use is to set a variable inertia, for example one which scales with velocity as shown in FIG. 21. This inertia scaling creates the reduced impact force seen in FIG. 22.
Other means to reduce the impact force include controlling momentum rather force, using damping to absorb elastic energy, using negative stiffness to cancel bounce, and/or any other actively controlled means. We could set effective high inertia on change in direction to bleed off bounce energy. We could control momentum by zeroing out effective momentum on changes in direction. We could set controlled stiffness, damping and inertia as a function of position velocity and/or force to address the issue.
In addition, a model of muscle such as the 3 element Hill Model may be useful. The model could be inverted such that the effect forces would have on passive tissues/springs could be calculated. Then forces would be applied by the actuator to attempt to prevent energy storage in the passive tissues.
In another embodiment, transient force control may be used to apply transient forces greater than normal throughput the routine, possibly randomly. A force blip of this sort may help to tear and thus build muscle while the user is already at their maximum sustainable force.
Further, an application programming interface may be provided such that personal trainers and users can program in their own routine. This routine could use any number of previously mentioned controllers.

Inter-Rep Control Strategies

This section refers to strategies that are used to string together multiple reps into a set. Other control features will include the ability to change control force between repetitions or sets. For example, force might taper with progressing repetitions or sets to attempt to keep the user at maximum ability.
Pre-programmed warm-up routines will help prepare the user for higher loads. These routines are also useful for quick workouts, demos, and fitness tests.
In a tempo training program, the controlled exercise machine 10 will encourage the user to maintain a specific movement tempo. Visual, audio, or haptic feedback will help the user adhere to a given tempo by providing cues. A display timer will also demand a certain amount of rest between sets.

Muscle Confusion

Muscle confusion training is also provided by the controlled exercise machine 10. Exercise parameters would change on a per repetition, per set, per workout, or cross-workout basis so that the user would not know what exercise to expect. The machine might present 3 reps with high force towards the top of the travel range and 3 reps with high force towards the bottom of the travel range. Again a programming interface is provided for users and trainers to set up their own inter-rep routines for infinite variations.

Other Concepts

Other features of the controlled exercise machine 10 include data analytics collection. For example, user action may be converted into metrics describing their force, position, speed and related values. During the use of the system, analytic data generated by the system is stored. This stored data captures the characteristics of the workout. This data can then be analyzed en masse to determine commonalities from which one can derive the principle components of effective techniques. Further muscle performance may be tracked such as speed vs. force vs. position.
The controlled exercise machine may detect weak spots and use those weak spots to predict injuries before they occur. Workout routines can specifically target weak spots. Multi-axis force sensors may be used to monitor force on each limb and force direction to identify favoring and/or joint alignment problems.
The controlled exercise machine 10 may further be in electronic communication with a database for collecting multi-user data. The controlled exercise machine may bin users into categories in how they react to strength training. Data may be used to find out what types of workouts are working best for different bins.
Single user data may also be collected to display previous workout information on a display of the machine and used to encourage a user to best previous workout values.
An application program interface (“API”) may be provided to create workouts. Trainers may sell workouts in an application store environment and the workouts may be compatible with the controlled exercise machine 10. Users or trainers may share workouts with friends, or initiate challenges which may be in the form of games.
Data from the controlled exercise machine may also be utilized for gym scheduling. Multiple users may schedule use of the device, and sets may be scheduled to alternate with other users. Users selects to start a workout and then is scheduled to go through a series of exercises which will not interfere with other users. May have to wait for a time slot to be available.

Safety

Various safety features may be included on the force controller for controlling the controlled exercise machine such as voice shutoff, automatic shutoff, automatic decrease in force, variable inertia, muscle tuning as described above, vision, and personal customization.

Motivation

A key requirement for achieving fitness is to maintain motivation. This machine will include a user interface which helps motivate users to bring to the gym and complete their exercises.

Muscle Model and State Testing

In one embodiment, the controlled exercise machine of the present disclosure may be used to determine an individual's muscle model and muscle state. During an exercise, the actuator may apply a small, nearly instantaneous perturbation in force experienced by the user. The perturbation in force applied on the controlled exercise machine on the user may take the form of a step increase or decrease in force by approximately 10%, and may remain at that level for a period of between 10 ms and 1 second before returning to an initial value as shown in FIG. 23.
A response of the user to the force perturbance is determined by detecting a change in position of the user output arm 12 in response to the perturbance. As shown in FIG. 24, near instantaneous changes in position (less than 50 ms) due to change in force that align with the perturbance are detected. By measuring the instantaneous change in position due to the force perturbance, a muscle's stiffness may be sampled and otherwise analyzed, which is a function of both a strength of the muscle and its activation level. By analyzing instantaneous changes in velocity and position, muscle damping parameters may be identified. When observing position and velocity changes on a scale greater than 50 ms (FIGS. 25 and 26), a neurological muscle control model may be obtained which provides insight into the individual's mental state during an exercise. Both physical and muscle properties and a neural model may be used to tailor an exercise routine both on an inter-rep/inter-set control basis and on a long term training strategy basis using the control method described herein.

Example Machine

An actively controlled, actuated exercise machine for strength and/or rehabilitation is provided. The machine uses an actuator that is connected mechanically to an output arm. The user applies force to the output arm to conduct exercises. The machine incorporates sensors which sense the state of the sys-tem, useful for actively controlling the actuator as described above and collecting information as described above. Nominally those sensors are either position/velocity sensors that measure either the position/velocity of the actuator or position/velocity of the output arm or they are force sensors which measure force applied by the user or force output by the actuator. The system includes an actuator controller that reads values of the sensors and applies active control to the actuator based on the readings.
An example machine, which has chest press exercise functionality is shown in FIGS. 1 and 2. However, the machine could be any number of other arrangements to exercise other muscles or other standard exercises. The machine could also be multiple degree of freedom in order to provide more variable trajectories and/or free/floating degrees of freedom. The additional degrees of freedom could be underactuated, fully actuated, or overactuated. Examples of other exercises to perform could be leg press, shoulder press, ab crunch, leg extension, leg curl, biceps curl, triceps extension, back extension, leg ab/adduction, and calf raise as examples.
The example machine of FIGS. 1 and 2 uses a motor coupled to a ballscrew for actuator. The ballscrew is connected to a pin joint would moves the output arm. The output arm is constrained to rotate around a pin joint with respect to the ground/base frame and thus has a single actuated degree of freedom. The user sits in the seat and pushes on the output arm producing a chest press exercise. An absolute encoder positioned at the arm/ground joint measures arm position for use with control algorithms and data collection. A force sensor is located so as to measure the force output of the actuator/the force output of the person for control algorithms and data collection.
Other various features may include a log-in system that allows the user to both recall and save data specific to the individual's use of the machine. The login mechanism can include wireless, contactless communication via an RF signal. The RF scheme may be, but is not limited to Near Field Communication (NFC), 802.11 wi-fi, RFID, or similar technology. Other methods include magnetic stripe, magnetic key, or a PIN code input. The login mechanism could be provided by a user's phone or by a supplied tag that could be inserted into a wrist mounted holder.
The controlled exercise machine 10 may include powered adjustable machine settings—seat height, arm width, leg length, etc. that move automatically when user logs into machine. By associating the user log-in data with known traits of the user, the machine is able to automatically initialize and configure itself in a manner conducive to the individualized use of the specific person who is logged in. These settings can include but are not limited to the height, weight, force, and mode of operation. These overall settings can be further adjusted on an individual machine, such that exact preferences can be stored on a per-machine basis. For example, the initial length of an arm grasp can be set for that user. Further, the machine can adjust the display to a position that provides an ergonomic comfort to the user.
To improve the system of the device, the user will have several mechanisms to immediately control the dynamics of the machine. One way is to have an emergency stop button. This “E-stop” button, accessible at all times, has the effect of shutting down the applied force of the system. Another approach is to have a soft stop available by voice command. This would allow the user to shut down the applied force by speaking a specified command, which would be received by a microphone on the machine and translated into a command to stop the force. To prevent errant behavior from other nearby users, the microphone system could consist of an array of microphones to localize the voice command to the intended range of an active user of the machine.
In operation, a user is seated on the controlled exercise machine 10 and engages the grips 22A and 22B of the output arm 12. As the user places a force on the user output arm 12, that force is detected by the force sensor and received on the force controller. The force controller detects the force, and further detects a position and velocity of the output arm using the encoder. Depending on a desired workout to be performed, in response to the detected force, position, and velocity, the force controller activates the actuator to impart a force on the output arm to create desired resistance for the user. The force controller continues to run a feedback loop in which parameters are continuously evaluated and a force provided by the actuator adjusted to maintain the force experienced by the user within a desired range.
The controlled exercise device of the present disclosure advantageously provides a dynamic adjustment of force on a user during a workout to optimize strength training of the user. Depending on the desired workout, the actuator is activated by the force controller in response to detected force, velocity and position data. Because the force may be varied by the actuator without the necessity of additional weights, an overall weight of the machine may be reduced compared to traditional weight exercise machines.
The foregoing description of preferred embodiments of the present disclosure has been presented for purposes of illustration and description. The described preferred embodiments are not intended to be exhaustive or to limit the scope of the disclosure to the precise form(s) disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments are chosen and described in an effort to provide the best illustrations of the principles of the disclosure and its practical application, and to thereby enable one of ordinary skill in the art to utilize the concepts revealed in the disclosure in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the disclosure as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

Claims

What is claimed is:

1. An actively controlled exercise device comprising:

a user output arm movably attached to a base frame and movable in at least a first exercise direction and a second exercise direction, wherein the first exercise direction corresponds to concentric work of a muscle of the user and the second exercise direction corresponds to eccentric work of the muscle of the user;

an actuator attached between the user output arm and the base frame, the actuator including a motor and an output shaft connected to the user output arm;

at least one position sensor attached to the actively controlled exercise device adjacent to the user output arm for detecting a position and velocity of the output arm;

a load cell attached to the actively controlled exercise device adjacent to the actuator for detecting a force exerted on the user output arm; and

a force controller in communication with the position sensor, the load cell, and the actuator for receiving data from the at least one sensor attached on the actively controlled exercise device and, in response to position, velocity, and force data received from the position sensor and load cell, activating the actuator to impart a force on the user output arm during an exercise repetition.

2. The actively controlled exercise device of claim 1, wherein the actuator comprises a linear actuator.

3. The actively controlled exercise device of claim 2, wherein the actuator comprises a ball screw linear actuator.

4. The actively controlled exercise device of claim 1, comprising both at least one encoder sensor and one force sensor, wherein the force controller activates the actuator based on data detected by both the force sensor and encoder sensor.

5. The actively controlled exercise device of claim 1 wherein the position sensor comprises an absolute position encoder.

6. The actively controlled exercise device of claim 1, wherein the force controller instructs the actuator to impart a force in the second eccentric work direction that is greater than the force imparted on the first concentric work direction.

7. The actively controlled exercise device of claim 1, wherein the force controller activates the actuator to impart a ramped force on the user output arm such that the force is at a minimum when velocity is detected as zero and gradually increases when velocity is detected as being greater or less than zero.

8. The actively controlled exercise device of claim 1, wherein the force controller activates the actuator to impart a positive force when the position sensor detects the user output arm to be at a first position, and wherein the force controller activates the actuator to impart a negative force when the position sensor detects the user output arm to be at a second position.

9. The actively controlled exercise device of claim 1, wherein the force controller activates the actuator to move the user control arm along a fixed position and time path, and wherein data related to a force of the user on the user control arm is detected by the load cell adjacent to the actuator.

10. The actively controlled exercise device of claim 1, wherein the force controller imparts a short perturbance force on the actuator during an exercise and detects a position and velocity response of the user through the user output arm.

11. An actively controlled exercise device comprising:

a force controller comprising a processor and computer readable storage and in electronic communication with the actuator, position sensor, and load cell, the force controller including one or more instructions executable on the processor for:

detecting position, velocity, and force data from the position sensor and load cell;

in response to detected position, velocity, and force data, activating the actuator to impart a force on the user control arm; and

adjusting a force imparted on the user control arm based on one of a detected position, force, and velocity of the user control arm.

12. A method of actively controlling an exercise device, the method comprising:

providing a user output arm movable in relation to a base frame;

providing at least one encoder sensor and force sensor in communication with the user output arm for detecting a position and velocity of the user output arm and a force imparted on the user output arm;

providing an actuator in mechanical communication with the user output arm;

providing a force controller in electrical communication with the encoder sensor, force sensor, and actuator;

detecting a position and velocity of the user output arm with the encoder sensor;

detecting a force exerted on the user output arm by a user with the force sensor;

activating the actuator to impart a force on the user control arm based on a detected position, velocity, and force of the user control arm, wherein the force is greater when the user control arm is determined to be moving in an eccentric work direction and less when the user control arm is determined to be moving in a concentric work direction.