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Automation and motion control technology has been widely used throughout industry for many years, becoming ever more sophisticated in its ability to deliver real performance and productivity benefits to companies in sectors ranging from automotive to aerospace. In the healthcare sector, however, the use of automation technology has been limited, finding application mainly in areas such as the production line manufacture of medical equipment and in labour intensive and repetitive laboratory based micro-array or other analysis processes. In the front line areas of hospitals and medical facilities, however, there has until recently been little wide-scale uptake in the use of automation or motion control devices, despite the extremely complex and sophisticated nature of many of the equipment and systems employed.
As a technology or process, however, automation has much to offer hospital staff and patients alike, creating the opportunity to improve the functionality, ease of use and reliability of many different systems, from beds and couches to surgical equipment, scanners and imaging machines.
Perhaps as importantly, partial or full automation of medical systems linked to appropriate monitoring and control mechanisms can help to make tasks such as patient lifting or hoisting far simpler, while increasing the availability and operating life of equipment, often with a corresponding reduction in costs as maintenance intervals can either be extended or at least planned far more efficiently.
It is important to recognise that automation and motion control need not necessarily imply highly complex and therefore expensive technology.
Indeed, the vast majority of automation and motion control mechanisms are relatively simple, low cost devices that are used either as stand alone items or integrated into wider control or monitoring networks.
In particular, applications that traditionally have been seen as low-tech, such as power actuated beds, couches and patient lifts and hoists, are now benefiting from a new generation of inexpensive actuation products that enable hospital managers and maintenance staff to ensure that each device is safe and, perhaps as importantly, to maximise the use and availability while minimising operating costs.
Beds are perhaps one of the most common yet most important items of equipment in any hospital, with availability being a key requirement in the day to day planning and the ability of each ward or department to process patients quickly without affecting the quality of service.
Although the King's Fund bed has been widely used for many years it has more recently been steadily replaced or supplemented by a new generation of profiling or variable posture beds, which are electrically adjustable to offer patients increased comfort and independence, and to reduce the workload of ward staff by minimising manual handling of patients and the risk of back pain or injuries.
Movement of the different sections of each bed is generally achieved by means of electrically driven actuators, mounted to the bed frame or a two, three or four position mattress platform, with the number of actuators varying according to the required functionality of each bed.
Typically, there can be up to seven devices controlling height and rake adjustment of the backrest and knee break, lateral turn and tilt for postural therapy, and longitudinal tilt for Trendelenberg and Reverse Trendelenberg positioning for various emergency or therapeutic situations.
Patient hoists and lifts also use similar methods and devices to raise, lower and move patients into appropriate positions for subsequent treatment or transfer to other equipment.
In each case, however, the key to the reliable long term operation of the equipment is the performance and functionality of the various actuators.
Generally, these are constructed from a motor driven ballscrew or cylinder and piston arrangement, with the component metal parts being manufactured from either high grade or stainless steel for optimum strength, hygiene and operating life.
Standard features typically include mechanical end stops, encoders, limit switches, anti-jamming mechanisms and overload protection.
Although these devices are generally extremely reliable and hard wearing there are instances where they can fail unexpectedly, usually because they have reached the limit of their operating life.
Although equipment manufacturers will build in failsafe mechanisms, with an actuator that fails normally locking itself into place, the result is that equipment becomes unusable and has to be taken out of service, reducing availability and, in the case of a bed, leading to the cancellation of a hospital appointment or a reduction in patient service.
Perhaps as importantly, according to a report published by the Medicines and Healthcare Products Regulatory Agency (MHRA), an executive agency within the UK Department of Health, electrically operated patient hoists pose a serious risk within the health sector if they fail while a patient is being carried.
The MHRA document highlights that the key issue is the unpredictability of the condition and service life of each electric actuator, and that the life of a hoist actuator is not dictated by its age but predominantly by its duty cycle; ie the number of times it is lifted and lowered.
In addition, the report states that establishing the life of an actuator is difficult because hoists do not have counters fitted to record the number of lifting cycles, and therefore recommends that equipment inspections should take place at least every six months; this process demands, however, that the bed is taken out of service and requires the time and skills of dedicated service or maintenance staff.
To overcome this problem a new generation of actuators has been introduced, which incorporate simple but highly effective monitoring technology.
In essence, each actuator has an integrated ASIC microchip that measures the time during which the actuator motor operates.
By automatically comparing the period for which the motor has run in total against predefined algorithms or models for all operating conditions, ranging from no load to full load, the ASIC is able to record the repeated use of the actuator and therefore to predict its remaining safe operating life.
In practice, the longer the duration of the motor run sequence, the higher the load will have been.
Further lifetime monitoring data is provided by recording the temperature at which the motor has been operating.
For example, hoist actuators should never be used continuously since the motors are started under full power to give peak torque and therefore become hot very quickly.
Excessive motor heat is recorded by the monitoring chip indicating that the actuator has been subjected to abuse, thereby shortening its life expectancy by known proportions.
The lifetime monitoring system uses a simple traffic light style display on the housing of each actuator to indicate the current status of the actuator when in use: a green LED shows that the unit is within 0-80% of its predicted life; an amber LED shows 80-90% of calculated life; and a red LED for over 90% of calculated life.
An optional buzzer can also be incorporated in case the actuators are mounted in such a way that the LEDs are hard to see, alerting operating staff when the calculated life reaches 90% and allowing time for planned service or replacement before a sudden failure occurs that would render a patient bed unserviceable.
Measuring just 25 x 35mm, the miniature PCB on which the ASIC is mounted fits within the existing actuator housings and therefore does not affect the footprint of actuators, allowing them to be retrofitted to existing equipment.
Similarly, the incorporation of a microchip enables each actuator to be easily connected to a PDA, laptop or even a mobile phone, to which the captured data can be downloaded for further analysis either directly or via a wireless link.
Using windows-based software this allows a range of factors to be analysed including total number of stokes, max over temperature for each movement and over voltage.
In addition, the software allows each the serial and batch number of each actuator to be logged, improving both quality control and local bed management if maintenance teams need to swap actuators from bed to bed.
Although there are other methods of monitoring actuator life, these typically use a device incorporated in a control box, which is connected to two or more actuators.
As a result, if actuators are switched over during routine maintenance, something that frequently occurs when maintenance staff are under pressure to make as many beds, hoists or other items of equipment available, it is necessary either to swap all actuators and their associated control box together or to keep a separate record of each individual actuator in order to predict its operating life.
By comparison, by integrating the monitoring chip within the actuator, it ensures that all data remains with the device throughout its operating life, making maintenance and replacement far simpler and less costly.
Additionally, as there are no magnetic or electromagnetic components used there is no risk of interfering with other medical equipment.
Although actuators are most widely used in beds, hoists and other ward equipment, they also form part of larger automation and motion control systems found in the latest scanners and diagnostic tools.
For example, combining actuators, telescopic columns and pillars, with motors, gearing mechanisms and sophisticated control devices enables scanning heads, patient tables and combined HMI and monitor units to be positioned smoothly, efficiently and, as importantly, with considerable accuracy and repeatability, often to within a few microns.
In addition, these motion control devices can be integrated into higher level systems, such as patient positioning tables linked to imaging and kidney stone dissolution machines, for kidney stone and urology treatment.
Regardless of the degree of sophistication of the automation system, it still depends on the reliability, performance and functionality of the mechanical or electro-mechanical devices that position and control each moving part of the operating system.
Indeed, such is the functionality of many of the latest devices that they can be used almost as self-contained automation units in their own right, ready for connection to higher level monitoring and control systems without the need for a conventional PLC control hierarchy.
In many respects, automation holds the key to the future developments within the medical and healthcare sectors, creating the opportunity for manufacturers and end users alike to improve the performance, functionality and reliability of medial equipment and systems, without affecting operating and maintenance costs.
In addition, greater use of automated equipment will help healthcare professionals improve their working conditions, make better use of staff time and resources and reduce the incidence of work-related injuries.
| Product Model | Inside Diameter | Outside Diameter | Thickness |
| ZMA50/92 bearing | M50X1.5 | 92 | 32 |
| ZMA50/75 bearing | M50X1.5 | 75 | 25 |